Future Small Arms Requirements WBE 2.4 Load Balance and Support in Weapon Design Manipulation of Weapon Weight and Centre of Mass About the Vertical (Z) Axis

Jose Peralta-Huertas Alexi Natale Jonathan Honey DRDC – Toronto Research Centre

Defence Research and Development Canada Scientific Report DRDC-RDDC-2016-R176 August 2016

IMPORTANT INFORMATIVE STATEMENTS

In conducting the research described in this report, the investigators adhered to the policies and procedures set out in the Tri-Council Policy Statement: Ethical conduct for research involving humans, National Council on Ethics in Human Research, Ottawa, 2014 as issued jointly by the Canadian Institutes of Health Research, the Natural Sciences and Engineering Research Council of Canada and the Social Sciences and Humanities Research Council of Canada.

Template in use: (2010) SR Advanced Template.dotm

© Her Majesty the Queen in Right of Canada, as represented by the Minister of National Defence, 2016 © Sa Majesté la Reine (en droit du Canada), telle que représentée par le ministre de la Défense nationale, 2016

Abstract

A laboratory study was undertaken at Defence Research and Development Canada – Toronto Research Centre (DRDC – Toronto Research Centre) during the period of 12 January to 6 March 2015. Thirty two (32) Canadian Armed Forces (CAF) personnel (male, aged 21 to 40) were asked to shoot a number of simulated serials using the surrogate test bed on an instrumented 8-metre-wide indoor firing lane. The test bed was initially configured to simulate a C7A2 in size, weight, and centre of mass (CoM). The test bed weight, and balance were varied systematically resulting in four configurations as follows: N: same weight as C7A2, CoM at the same location as C7’s; 1.5A: 1.5 kg heavier that N configuration, CoM above C7’s (about 5 cm); 3A: 3 kg heavier that N configuration, CoM above C7’s (about 5 cm); and 3B: 3 kg heavier than N configuration, CoM below C7’s (about 2 cm). This was done by manipulating the position of the bolt-on weights along the vertical (Z) axis through the theoretical CoM. The CoM was manipulated along the local coordinate system of the weapon. For every change to the weapon’s center of balance and weight, the participants shoots two 5-round groupings. Data collected consisted of 6 marksmanship metrics collected using the SCATT software that is a simulated marksmanship system. A significant difference was found in only one measure, the Mean Group Centre Radius, during the standing hold serial. This measure for N condition was significantly smaller than the one for 3A condition (p = .04). In contrast, all heavy configurations (1.5A, 3A and 3B) failed in Overall (Weight, Balance and Acceptance) factors according to participants. These findings may indicate that weight and CoM manipulations on vertical (Z) axis have minimal effect on marksmanship in spite of poor acceptance among shooters.

Significance to Defence and Security

As technologies advance, there is increasing interest to add systems like thermal sights and grenade launchers to small arms. This research advises the defence community of the potential effects, such as fatigue and discomfort using the weapon that auxiliary devices added to a conventional weapon can cause.

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Résumé

Une étude en laboratoire a été entreprise par Recherche et développement pour la défense Canada – Centre de recherches de Toronto (RDDC – Centre de recherches de Toronto) du 12 janvier au 6 mars 2015. On a demandé à 32 membres du personnel des Forces armées canadiennes (FAC) (hommes âgés de 21 à 40 ans) d’effectuer un certain nombre de séries de tirs simulés à l’aide du banc d’essai de remplacement dans un couloir instrumenté de tir intérieur de 8 m de largeur. Le banc d’essai a d’abord été configuré pour simuler un C7A2 en taille, poids et centre de masse (CoM). On a fait varier systématiquement l’équilibre et le poids du banc d’essai, ce qui a permis d’obtenir quatre configurations : N : même poids que le C7A2, CoM au même endroit que celui du C7; 1.5 A : 1,5 kg plus lourd que la configuration N, CoM au-dessus de celui du C7 (environ 5 cm); 3A : 3 kg plus lourd que la configuration N, CoM au-dessus de celui du C7 (environ 5 cm); et 3B : 3 kg plus lourd que la configuration N, CoM en dessous de celui du C7 (environ 2 cm). Cela a été fait en manipulant la position des poids à boulonner le long de l’axe vertical (Z) par le CoM théorique. Le CoM a été manipulé le long du système de coordonnées locales de l’arme. Pour chaque changement de poids et de centre d’équilibre de l’arme, les participants ont procédé à deux groupements de cinq tirs. Les données étaient composées de six mesures d’adresse au tir recueillies à l’aide du logiciel SCATT, qui est un système d’adresse au tir simulé. On a constaté une différence importante dans une seule mesure, le Mean Group Centre Radius, pendant la série de maintien debout. Cette mesure de la condition N était considérablement plus petite que celle de la condition 3A (p = 0,04). Par contre, toutes les configurations lourdes (1.5 A, 3A et 3B) ont échoué en ce qui a trait aux facteurs globaux (poids, équilibre et accueil), selon les participants. Ces constatations peuvent indiquer que la manipulation du poids et du CoM sur l’axe vertical (Z) a un effet minimal sur l’adresse au tir malgré l’accueil mitigé des tireurs.

Importance pour la défense et la sécurité

Au fur et à mesure que les technologies évoluent, on est de plus en plus intéressé à doter les armes de petit calibre de systèmes comme les lance-grenades et les viseurs thermiques. La présente recherche met la communauté de la défense au courant des effets potentiels des dispositifs auxiliaires ajoutés à une arme conventionnelle, comme la fatigue et l’inconfort.

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Table of Contents

Abstract ...... i Significance to Defence and Security ...... i Résumé ...... ii Importance pour la défense et la sécurité ...... ii Table of Contents ...... iii List of Figures ...... v List of Tables ...... vi Acknowledgements ...... vii 1 Introduction ...... 1 2 Methods ...... 2 2.1 General Overview ...... 2 2.2 Clothing ...... 3 2.3 Instrumentation...... 3 2.3.1 Manipulation of the CoM Along the Vertical (Z) Axis ...... 4 2.3.2 Weight Conditions (Total Weight of Weapon): ...... 6 2.4 Shooter System...... 7 2.5 Firing Serials ...... 8 2.6 Data Measures ...... 9 2.7 Test Protocol ...... 10 2.8 Statistical Analysis ...... 11 3 Results ...... 12 3.1 Objective Results ...... 12 3.1.1 Hold ...... 12 3.1.2 Pivot ...... 13 3.2 Subjective Results Questionnaire ...... 14 3.2.1 Overall Metrics ...... 15 3.2.2 Specific Metrics ...... 16 4 Discussion ...... 18 4.1 NATO RTO Implications ...... 19 5 Conclusion ...... 20 References ...... 21 Annex A Study Information Sheet ...... 23 Annex B Participant Information ...... 25 Annex C Configurations...... 29 Annex D User Acceptance Questionnaire ...... 31 List of Symbols/Abbreviations/Acronyms/Initialisms...... 33

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List of Figures

Figure 1: Modular weight, size and center of balance of the test bed concept. From Kelly et al. (2013)...... 4 Figure 2: Test bed with aluminum rig (frontal view)...... 5 Figure 3: Test bed with aluminum rig (lateral view)...... 5 Figure 4: Recommended CoM adjustability along (Z) axis for weapon test bed; modified from McKee and Tack (2009)...... 6 Figure 5: SCATT shooter system...... 7 Figure 6: Seven level Likert type acceptability scale...... 9 Figure 7: SCATT shooter training system and test bed setup...... 11 Figure 8: Overall acceptance metric rankings...... 16 Figure C.1: N configuration...... 29 Figure C.2: 1.5A configuration...... 29 Figure C.3: 3A configuration...... 30 Figure C.4: 3B configuration...... 30

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List of Tables

Table 1: Participant shooting and military experience...... 3 Table 2: Depiction of firing serials...... 8 Table 3: Marksmanship performance measures...... 9 Table 4: Descriptive statistics for the hold applications...... 12 Table 5: Descriptive statistics for the pivot applications...... 13 Table 6: Overall acceptance descriptive statistics...... 15 Table 7: Specific metric rankings distribution (Fail = Likert rating less than four). .. 16

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Acknowledgements

We would like to acknowledge the important contribution of Capt G. Pajuluoma to the technical design and data collection in this study. He also contributed extensively with the statistical data analysis.

One other major contributor was Ed Nakaza whose advice was pivotal for our understanding of the technical challenge that the study entailed. Special thanks to Jim Clark who contributed most of the report pictures.

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1 Introduction

The Future Small Arms Research (FSAR) program will support the Canadian Armed Forces’ (CAF) next generation small arms project by developing a validated, science-based Statement of Operational Requirements (SOR) for a weapon system that will increase accuracy and lethality while at the same time be completely integrated into the soldier’s protective system. The SOR will describe a suite of weapons that will enhance operational effectiveness while reducing the soldier’s cognitive and physical burden while allowing commanders a scalable response appropriate to the demands of the situations they encounter. Because weapon accuracy and overall lethality is so dependent upon the soldier and the integration of weapon and soldier, a significant component of the research conducted under the FSAR program is in the area of Human Factors (HF), being led by Defence Research and Development Canada – Toronto Research Centre (DRDC – Toronto Research Centre).

Physical Ergonomics in Weapon Design – Work Breakdown Element (WBE) 2.4 builds upon the work conducted under NATO RTO SCI-178/RTG-043 and an earlier FSAR study in June 2013 (protocol 2013-033) (Nakaza and Tack, 2013) to assess the impact of weapon physical factors on system performance. Using the physical ergonomics test bed as detailed by Kelly, Tack and Nakaza (2013), this experiment further investigated the effects of the weapon load and balance on target engagement performance. The current study followed similar methodology as Nakaza, Tack, Osborne and Zemsta (2014) regarding load and CoM manipulations in order to complement NATO RTO SCI-178/RTG-043. Nakaza et al. (2014) when tested CoM manipulations in the (X) axis indicated that weapon systems should avoid having a CoM located to the front and suggested that posterior studies should focus in configurations where the mass is located either in the centre or the back of the weapon. They indicated the need to explore a manipulation in the vertical axis.

One of the most recent approaches to identify factor affecting the manipulating the weight and center of mass (CoM) of a weapon was done by Stone et al. in 2014. This study compared a bullpup configuration to a conventional one in regards of stability and shooting accuracy. The findings of the paper suggested that the stability of the shooter enhanced his/her performance. The authors attributed the greater stability of bullpup configuration to its short length and the proximity of the trigger to the user. The current trend of adding devices such as grenade launchers and/or thermal sight could modify both the weight and the CoM of any weapon used in the CAF by altering the shooter stability.

The current project was focused on finding how the manipulation of the CoM and weapon weights on the vertical (Z) axis affected marksmanship performance. We anticipated that a manipulation of the CoM in the vertical would not alter shooter performance because the displacement of this point is within a few centimeters from the initial CoM, therefore the effect on shooter stability would be minimal.

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2 Methods

2.1 General Overview

A laboratory study was undertaken at DRDC – Toronto Research Centre during the period of 12 January 2015 to 6 March 2015. Thirty two (32) CAF personnel (male, aged 21 to 40) were asked to shoot a number of simulated serials using the test bed on a 3-metre-wide instrumented firing lane located within an auditorium (described in Section 2.3, Figure 1). The test bed was configured to simulate a C7A2 rifle in size, weight, and center of mass. Using this test bed, the soldiers first shot two training serials. Each serial consisted of a 5-round grouping, fired while in the standing position. These two 5-round groupings were to familiarize the shooter with the size, shape, and weight of the test bed. After shooting each 5-round grouping, feedback was provided to the shooter to improve accuracy with the test bed. Extra rounds were shot if the participant needed. Following this training serial, the shooter shot four 5-round groupings, which represented the test condition. The test bed weight, balance, and size were varied systematically. This was done by manipulating the position of the bolt-on weights along the (Z) axis (through the theoretical CoM) (see Section 2.3.2). For every change to the weapon’s CoM the participant shot four 5-round groupings. Data collected consisted of grouping size, point of impact (POI), accuracy relative to the center of the target and muzzle track relative to the center of the target. The methods are described in greater detail below.

Participants were recruited using Canadian Forces Task Planning and Operations (CFTPO) processes and were drawn from 1RCR, 2RCR, 3RCR and Reserve units from Toronto. Although tasked to the project, all potential participants were informed that their participation was voluntary and that they could withdraw from the study at any time without penalty or repercussions. Participants were males, between the age of 21 and 40, all trained and experienced shooters. Participants did not have any medical limitations to deployment. Participants were asked not to exercise within the 12-hour period preceding participation in the study in order to reduce the impact of muscle fatigue (Annex A). Participant characteristics (demographic data) and visual acuity data were collected under protocol 2013-065: Omnibus Protocol for all Studies Run during the 2015 Winter Experimentation Campaign via questionnaire (Annex B) are depicted in Table 1. Each participant was also given a unique, non-identifying number. After shooting a serial a questionnaire was given to subjects to evaluate their experience with the particular serial (Annex D).

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Table 1: Participant shooting and military experience.

Rank Level Marksmanship Level (n) Military Experience (n)

Junior NCM PWT 2: 1 < 2 years: 2 PWT 3: 2 2–5 years: 8 PWT 3 Supplement: 10 5–8 years: 8 PWT 4: 8 8–11 years: 7 PWT 4 Supplement: 6 11 + years: 1 PWT 5: 1 Reserve (2–11+y): 5 Senior NCM PWT 3 Supplement: 2 11 +years: 2 PWT 4 Supplement: 1 Reserve (5–8 y): 5 Missing Data 1 1 Total 32 32

2.2 Clothing

Participants conducted the experimental protocol while wearing Full Fighting Order (FFO). This consists of the following: Clothe the Soldier Canadian Disruptive Pattern (CTS CADPAT) combat clothing; combat boots; CG634 combat helmet; fragmentation protective vest (FPV); tactical vest (with standardized combat load consisting of four magazines, two simulated smoke grenades, two simulated fragmentation grenades, one Personal Role Radio, one first aid kit, and one full canteen); combat gloves; and ballistic eyewear.

2.3 Instrumentation

A prototype physical ergonomics test bed, designed to accurately represent and measure the effect of weapon size, weight, and balance on a soldier’s ability to aim and shoot, has been designed and built. The test bed consists of a set of aluminum channels that can be fitted with handgrips, magazine wells, NATO standard rail systems, weapon sights, and differing butt stocks (Figure 1). The test bed has a functional trigger that, when depressed, activates an electric solenoid to provide recoil. Weapon weight and balance can be adjusted using bolt-on weight plates of varying size and material composition. The test bed was fitted with a sensor suite that provides data on

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weapon position, aim point, and the location of a simulated shot when fired. Part of the sensor suite involves an eye-safe laser emitter mounted on the test bed. An electronic target tracks the point of aim of the weapon, and registers the point of impact when the test bed trigger is pulled (a simulated “shot”). This system has been developed to train Olympic biathlete sharpshooters and is marketed and sold by SCATT, Shooter Training Systems (www.scatt.com). Using this system, the effect of systematic variation in weapon size, weight, and center of mass of the test bed on shooter performance can be accurately measured.

Figure 1: Modular weight, size and center of balance of the test bed concept. From Kelly et al. (2013).

The test bed was fitted with a C79 sight mounted on a NATO standard rail, with the C79 sight range selector set to the shortest range setting. The test bed sensor and C79 sight was zeroed by the participant on a fixed tripod prior to the start of each application. The test bed configurations consisted of the following conditions.

2.3.1 Manipulation of the CoM Along the Vertical (Z) Axis

In order to manipulate the loads along the vertical axis, an additional rig was built with aluminum channels (Figure 2 and Figure 3). The rig vertical pieces were aligned to the theoretical CoM of a C7A2 rifle on the longitudinal (X) axis according to (McKee and Tack, 2009) (Figure 4). The device was implemented for all configurations except N configuration.

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Figure 2: Test bed with aluminum rig (frontal view).

Figure 3: Test bed with aluminum rig (lateral view).

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2.3.2 Weight Conditions (Total Weight of Weapon):

The following weights were calculated as if a conventional C7A2 rifle were combined with an infrared sight on top and a grenade launcher underneath (McKee and Tack, 2009): 3.9 kg (Current C7A2 rifle) as configuration N (with no aluminum rig); 5.4 kg (C7 + Infrared sight) as configuration 1.5A (with rig); and 6.9 kg (C7 + Infrared sight + M203 grenade launcher) as configuration 3A (manipulation “Above” the theoretical CoM) and 3B (manipulation below the CoM). Both configurations were built with rig (see Section 2.3.2).

Vertical (Z) axis 5 cm Above CoM (1.5A & 3A Configuration)

CoM

Z=0 (N Configuration)

2 cm Below CoM (3B Configuration)

Figure 4: Recommended CoM adjustability along (Z) axis for weapon test bed; modified from McKee and Tack (2009).

Centre of Mass locations and calculations from different configurations were found following two approaches: the experimental method and the mathematical approach. The experimental method determines the CoM by suspending the objects from two or more locations and drop plumb lines from the suspension points. The intersection of the lines is the Centre of Mass (Kleppner and Kolenkow, 1973). The mathematical method considers different segments and masses. This can be applied to the test bed and aluminum rig. Knowing the distance to a reference point and the mass of the segment the torque can be calculated for every segment and for the whole structure by adding partial torques and dividing the total torque by the total mass of the object. Therefore, the CoM in the X (longitudinal) axis of the weapon is:

CoM=m1x1 + m2x2 + ---- + mnxn /M (Taken from Spark Notes).

Where m1 is the mass of the first segment, x1 is the length from one segment to the other, and M is the total mass (weight).

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Accordingly, the CoM in the Z (vertical axis) is:

CoM=m1y1 + m2y2 + ---- + mnyn/M (taken from Spark Notes).

The resulting four configurations (Annex C) were: N: same weight as C7A2, CoM at the same location as C7’s; 1.5A: 1.5 kg heavier that N configuration, CoM above C7’s (about 5 cm); 3A: 3 kg heavier that N configuration, CoM above C7’s (about 5 cm); and 3B: 3 kg heavier than N configuration, CoM below C7’s (about 2 cm).

2.4 Shooter System

To capture objective shooting performance data (i.e., shot location, shot grouping, and muzzle trace), the physically ergonomic test bed was equipped with the SCATT WS1 Shooter System. The system is a training tool used for competitive shooters. It gives users the possibility to practise in average-size room with any kind of weapon and simulate shooting distances up to 1000 m. It consists of three main components as follows: an electronic optical sensor that is fixed to the barrel of the weapon; an electronic target and; software that displays on the computer screen the “calibration” and the impact points after activating the trigger as well as the trace followed by the barrel before and after the shot (Figure 5).

Figure 5: SCATT shooter system1.

1 Image taken from http://www.scatt.com/products (Access date: 11 May 2015).

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2.5 Firing Serials

The following are the serials that shooters conducted (Table 2). All serials were conducted in the standing firing position. Once the shooter achieved a comfortable standing shooting position during the training serial, the shooter’s hand position on the test bed was kept constant for Serials 3 to 5.

Table 2: Depiction of firing serials.

Serial No Title Repetitions Rounds Description

1 Training 2 5 Adopting the standing posture, the shooter fired as many shots until they reached a level of comfort and familiarity with the size, shape and weight of the test bed. 2 Standing 2 5 Adopting the standing posture on “TARGET” Hold command, the shooter was asked to sight on the center of the target and to hold the weapon in position for 10 seconds. Then, without lowering the weapon on “FIRE” command, the shooter fired a single shot aiming for the center of the target. The shooter lowered his weapon and repeated the task after a 10-second rest. After a 5-round grouping was completed, the shooter was given 1-minute rest and this application was repeated. 3 Pivot 2 5 Adopting the standing posture, the shooter began by facing 90° from the target (e.g., present left shoulder to the target). At the command of “TARGET” the shooter turned to face the target, and when comfortable fired a single shot aiming for the center of the target. The shooter returned back to the initial posture and repeated the task after a 10-second rest. After a 5-round grouping was completed, the shooter was given 1-minute rest and this application was repeated.

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2.6 Data Measures

Objective measures consisted of the following:

Table 3: Marksmanship performance measures.

Measure Definition

Track Length The path length taken by the aiming trajectory during the (Trajectory Length) period between actual shooting and one second prior to the cm shot (averaged from SCATT export Excel file and converted from mm to cm).

Mean Radius Averaged radial distance of each shot from target centre. cm

Mean Group Centre Radius Averaged radial distance of each shot from the group centre. (Precision/Consistency) cm

Group Offset (x) (horizontal) Averaged offset of the group from target centre in x (Lateral cm Direction).

Group Offset (y) (vertical) Averaged offset of the group from target centre in y (Vertical cm Direction).

Absolute Offset Radial distance from group offset (x, y) to target centre. (Accuracy) cm

Participants completed the single page questionnaire at Annex D, following each test condition. The questionnaire consisted in 14 items evaluating user acceptance for every configuration based on a Likert seven points scale (Figure 6).

Figure 6: Seven level Likert type acceptability scale.

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2.7 Test Protocol

The following protocol was adhered to during this experiment:

1. The SCATT target was set up 8 m away from the firing line, and the centre of the target was located approximately 140 cm from the floor and leveled. SCATT Shooter Training System software version 6.65.00 was set up on a laptop and the 25 m Rifle (5.6 mm) (SBR25) standing shooting event was selected for all serials. Two parallel firing lanes were set-up in the classroom. No live rounds were fired.

2. The ergonomics test bed was configured to the test condition based on the order of presentation of conditions and secured in a gun rest (Magnum DeadShot FieldPod Tripod, Model 488111, USA) and adjusted level to the natural eye height of the participant (Figure 7).

3. The participant was briefed on the protocols for zeroing the test bed and training serial, the 10-second hold drill and the pivot drill.

4. The participant zeroed the test bed while it was secured in the gun rest.

5. The participant was instructed to take the test bed out of the gun rest, and perform as many practice shots (Serial 1 in Table 3) while adopting the standing posture. No time limit was given for this task and the participant was provided feedback after each shot was taken.

6. The participant was instructed to begin the 10-second hold drill (Serial 2 in Table 3).

7. The participant was instructed to begin the pivot drill (Serial 3 in Table 3).

8. The participant was requested to complete the Weight/Balance Questionnaire (located in Annex D).

9. The participant proceeded to the next firing lane where they repeated steps 3 through 8 using a different weapon configuration. The order of configuration was randomised

10. In the course of a day, each participant completed four testing conditions/configurations.

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Figure 7: SCATT shooter training system and test bed setup.

2.8 Statistical Analysis

All participants completed all four firing conditions: N, 1.5A, 3A, and 3B. Repeated Measures Analyses of Variance (ANOVA) was conducted for each shooting performance measure. Significant differences were identified at p < 0.05.

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3 Results

The results section details the objective data originating from the Hold and Pivot applications, and the subjective data originating from the questionnaire. The following section presents the objective and subjective results separately.

3.1 Objective Results

3.1.1 Hold

For the Hold applications, Track Length (cm), Mean Radius (cm), Mean Group Centre Radius (cm), Group Offset (x cm), Group Offset (y cm), Absolute Offset (cm), were calculated and are presented below. See descriptive statistics in Table 4.

For Mean Group Centre Radius, a significant effect was found between the four configurations: F(3, 124) =1.44, p=.36. Duncan’s post hoc analysis revealed that condition N (3.08 cm) had a significantly Mean Group Centre Radius smaller when compared to condition 3A (3.88 cm) Figure 8.

Table 4: Descriptive statistics for the hold applications.

Measure Configuration N Mean Std. 95% CI for Mean ANOVA Sig. (cm) Deviation (cm) Lower Upper Bound Bound

Track Length 3B 32 31.54 11.59 27.36 35.72 0.25 N 32 27.78 8.74 24.63 30.93 1.5A 32 31.08 10.12 27.43 34.73 3A 32 33.18 12.59 28.64 37.72

Mean Radius 3B 32 5.08 1.81 4.42 5.73 0.24 N 32 4.42 1.52 3.87 4.96 1.5A 32 5.12 1.42 4.61 5.63 3A 32 5.03 1.56 4.47 5.59

Mean Group 3B 32 3.80 1.17 3.38 4.22 0.04 Centre Radius N 32 3.08 1.17 2.66 3.50 1.5A 32 3.67 1.16 3.25 4.09 3A 32 3.89 1.27 3.43 4.35

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Measure Configuration N Mean Std. 95% CI for Mean ANOVA Sig. (cm) Deviation (cm) Lower Upper Bound Bound

Group Offset 3B 32 -0.64 2.61 -1.58 0.31 0.66 (X-Direction) N 32 0.07 2.13 -0.70 0.83 1.5A 32 -0.44 2.97 -1.51 0.63 3A 32 0.04 2.97 -1.03 1.11

Group Offset 3B 32 -1.29 2.47 -2.18 -0.40 0.99 (Y-Direction) N 32 -1.10 2.67 -2.07 -0.14 1.5A 32 -1.14 2.34 -1.99 -0.30 3A 32 -1.08 1.96 -1.79 -0.37

Absolute Offset 3B 32 3.23 2.07 2.85 4.10 0.85 N 32 3.12 1.69 2.70 4.14 1.5A 32 3.51 1.77 3.45 4.86 3A 32 3.24 1.74 2.75 4.26

3.1.2 Pivot

For the Pivot applications, Track Length (cm), Mean Radius (cm), Mean Group Centre Radius (cm), Group Offset (x cm), Group Offset (y cm), Absolute Offset (cm), were calculated and are presented below in Table 5.

No significant differences were found for the Pivot applications for these measures.

Table 5: Descriptive statistics for the pivot applications.

Measure Configuration N Mean Std. 95% CI for Mean ANOVA Sig. (cm) Deviation (cm) Lower Upper Bound Bound

Track Length 3B 32 40.35 13.03 35.66 45.05 0.10 N 32 35.89 10.04 32.27 39.51 1.5A 32 39.97 12.02 35.64 44.31 3A 32 43.99 15.63 38.36 49.63

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Measure Configuration N Mean Std. 95% CI for Mean ANOVA Sig. (cm) Deviation (cm) Lower Upper Bound Bound

Mean Radius 3B 32 5.72 1.73 4.42 6.34 0.53 N 32 5.37 1.69 3.87 5.97 1.5A 32 6.00 1.72 4.61 6.62 3A 32 5.75 1.67 4.47 6.35

Mean Group 3B 32 4.61 1.52 4.06 5.15 0.23 Centre Radius N 32 4.00 1.11 3.60 4.40 1.5A 32 4.31 1.17 3.88 4.73 3A 32 4.49 1.15 4.07 4.91

Group Offset 3B 32 -0.88 2.27 -1.70 -0.07 0.63 (X-Direction) N 32 -0.27 2.26 -1.09 0.54 1.5A 32 -0.35 2.84 -1.37 0.67 3A 32 -0.06 2.96 -1.13 1.01

Group Offset 3B 32 -1.51 2.68 -2.48 -0.54 0.84 (Y-Direction) N 32 -1.50 2.92 -2.55 -0.45 1.5A 32 -2.05 3.02 -3.14 -0.97 3A 32 -1.65 2.35 -2.50 -0.81

Absolute 3B 32 3.47 1.74 2.85 4.10 0.40 Offset N 32 3.42 2.00 2.70 4.14 1.5A 32 4.15 1.96 3.45 4.86 3A 32 3.51 2.10 2.75 4.26

3.2 Subjective Results Questionnaire

Participants expressed their rating of acceptability on fourteen metrics using the 7-point (Likert’s) scale. Metrics included; Speed of Target Engagement, Ease of Acquiring a Sight Picture, Time to Acquire a Sight Picture, Holding a Sight Picture, Controlled Firing, Pivoting to Fire, Hold Stability during Fire, Weapon Handling, Gross Aiming, Fine Aiming, Shot Release, Overall Weight, Overall Balance and Overall Acceptability. Participants were provided a section at the bottom of the questionnaire for open-ended comments.

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The results of the questionnaire are reported separately as three “Overall” metric ratings and the remaining eleven “Specific” metric ratings.

3.2.1 Overall Metrics

For the four conditions, a repeated measures ANOVA with a Green-Geissert correction of the Overall Metrics (Weight, Balance and Acceptance) ratings showed that the mean scores for the ratings were statistically different F(2.207,129.595)=39.322, p <.001.2 A post Bonferroni test evidenced that all configuration ratings were significantly different from each other (p <.001) with exception of N configuration compared to 1.5A configuration regarding Overall Balance and Overall Acceptance. Table 6 shows descriptive statistics for the Overall Acceptance rating.

Table 6: Overall acceptance descriptive statistics.

Overall Metric Mean Std. Deviation 95% Confidence Interval for Mean

Lower Bound Upper Bound

Overall Weight N 5.63 1.41 5.12 6.13

1.5A 4.65 1.52 4.09 5.20

3A 2.94 1.55 2.37 3.50

3B 3.39 1.78 2.73 4.04

Overall Balance N 5.56 1.24 5.11 6.01

1.5A 4.58 1.65 3.98 5.19

3A 3.29 1.68 2.68 3.91

3B 3.90 1.66 3.29 4.51

Overall N 5.59 1.10 5.20 5.99 Acceptance 1.5A 4.71 1.32 4.22 5.19

3A 3.52 1.48 2.97 4.06

3B 4.10 1.58 3.52 4.68

2 A non-parametric (Friedman’s) analysis was performed that showed a significantly difference between the three rantings (Overall Weight, Overall Balance, and Overall Acceptance) (X2(2, N=125)=164.98, p <.001. A Wilconxon Signed Ranks Test showed similar results as Bonferroni’s.

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In regards of Overall Acceptance, is evident that participants preferred N configuration over the others since most of their ranting are Likert level 4 or greater. See Figure 8.

All heavy configurations (1.5A, 3A and 3B) were considered fail regarding Overall Weight, Overall Balance and Overall Acceptance (1.5A Pass in Overall Weight) when responses were analyzed setting at Likert rating of 4 and up with 80% of participants in this category as Pass.

Overall Acceptance 3B 20 N

15 1.5A

10 3A

Frequency 5

0 1 2 3 4 5 6 7

Scale Ratings Figure 8: Overall acceptance metric rankings.

3.2.2 Specific Metrics

When responses were analyzed setting at a Likert rating of 4 and up with 80% of participants in this category as Pass, 1.5A and N configurations just failed in Weapon Length while 3A and 3B configuration obtained mixed result (see Table 7).

Table 7: Specific metric rankings distribution (Fail = Likert rating less than four).

Specific Rating/Configuration 1.5A 3A 3B N

Speed of Target Engagement Pass Fail Pass Pass

Ease of Acquiring a Sight Picture Pass Fail Fail Pass

Time to Acquire a Sight Picture Pass Fail Pass Pass

Holding a Sight Picture Pass Fail Fail Pass

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Specific Rating/Configuration 1.5A 3A 3B N

Controlled Firing Pass Fail Pass Pass

Pivoting to Fire Pass Fail Pass Pass

Stability During Fire Pass Fail Fail Pass

Weapon Handling Pass Fail Pass Pass

Weapon Length Fail Fail Fail Fail

Weapon Height Pass Pass Pass Pass

Weapon Width Pass Pass Pass Pass

Questionnaire comments from participants were grouped by configurations. Observations of 1.5A configuration included lack of handgrip, difficulty in keeping it steady, heavy weight affecting shooting, and device too heavy on the top and, bad balance. Regarding 3A configuration participants noted that the device was too heavy to hold for long periods, difficult to hold a sight picture because of its weight, similar to a gun machine, necessity of transferring weight to the front, short time for fatigue, weapon handling challenging, device too long, wrong balance and, hard turning and shooting with the test bed. 3B configuration comments included that the feeling of the weapon was heavier compared when weight was on top, target holding was challenging, it had better balance to keep a sight picture, its weight distribution was stable and, it was too heavy at bottom. Lastly, for the N configuration, comments were that the model was longer than the actual assigned weapon (C7A2), easier to hold and still and, that weight was preferred on the rear. Participants were informed that N configuration was similar to a C7A2 in weight but they were not informed of the weight of other configurations.

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4 Discussion

Thirty-two participants from the First, Second, and Third Battalion Royal Canadian Regiments (1RCR, 2RCR, and 3RCR) and members of Toronto Reserve units participated investigating the effects of the weapon load and balance on target engagement performance. A physical ergonomics test bed, similar in length to the in-service C7A2 rifle was used where the weight (3.9 kg, 5.4 kg, 6.9 kg) was systematically varied to the limits of design constraints and balance was varied in the vertical (or “y”) dimension based on reference from a theoretical digital modeling.

Results were similar for the four configurations both in the hold and pivot applications. Marksmanship markers analysis did not reflect any effect from weight and CoM variations in the vertical axis. The only exception was the Mean Group Centre Radius that was significantly greater in the 3A configuration compared to the N configuration in the hold application. These results may be interpreted as the manipulation of the vertical axis has no significant effect on shooting performance within the limits depicted above in a simulated environment.

In contrast, responses for the User Acceptance questionnaires, showed a different aspect of the study. When a Pass Acceptance criterion was set to a Likert rating of four and greater with 80% of participants in this category, conditions 1.5A and N were considered acceptable (Pass) in most of the markers while the heavier configurations like 3A and 3B were qualified as non-acceptable (Fail) in the majority of acceptance rankings. These markings may reflect that participants were not accustomed to the configurations at first, but their marksmanship experience and muscular strength kept their performance almost unaltered.

Marksmanship measures were taken following methods and instrumentation delineated in Nakaza et al. (2014). Our study found that Mean Radius in the Hold serial ranged from 1.48 to 9.08 cm while Nakaza’s reported a range from 5.13 to 6.04 cm. For the Offset in the longitudinal axis of the weapon (Y-Direction), we found a range of -8.00 to 4.79 cm while in the other study the measure ranged from -2.9 to -1.9 cm. Accordingly, Absolute Offset ranged from 0.40 to 10.18 cm in contrast to Nakaza range (2.95 to 3.75 cm). A similar agreement was found in the Pivot application. As expected, similar ranges in the marksmanship markers were found in the two studies but significant effects between weight conditions/configuration were found in Nakaza et al. (2014) while we identified just one difference between configurations in the hold serial. It may suggest than increasing loads in the -vertical (Z) axis (up to 6.9 kg) has no important implications in shooting performance. One possible explanation of this finding can be that the manipulation of the CoM in the configuration was close of the theoretical CoM of the weapon.

Acceptance questionnaire responses were similar when compared to Nakaza. Light weighted conditions like 3.9 and 5.4 kg were rated Acceptable in most of the ranking factors. However, participants evaluated the 5.4 kg configuration as Fail in two of three Overall rankings. Finding that may correspond to the level of acceptability to the same weight condition in Nakaza et al. (2014), report. In contrast, the heavy-weighted configurations (3A and 3B) where the total weapon weight was 6.9 kg, the majority of the responses were judged as Fail (Non-acceptable). This trend agreed with other studies, where 6.9 kg seems to be out of the limits of shooter acceptance. On the other hand, manipulation of CoM within the longitudinal (X) axis in prior studies suggested that displacing the CoM further away (to the barrel or the butt of the weapon)

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are not preferred by participants. Again, our manipulation of the CoM was small (5 cm above and 2 cm below the weapon CoM) that slightly affected shooting but it modified acceptance. Participants’ comments indicated that the test bed could be more realistic if some auxiliary pieces/devices are adapted to it. Handgrip or a similar device would be a valuable addition as well as a pistol trigger that simulates the same positions as a C7A2’s trigger.

4.1 NATO RTO Implications

The current study adds valuable information to the matrix cited in Nakaza et al. (2014). Weapon configuration with weights of 3.9, 5.4 and 6.9 kg may be manipulated in the vertical (Z) axis, with minor implications on shooting performance, if the CoM is collocated perpendicular (displaced within 5 cm above or 2 cm below) to the theoretical C7A2 rifle CoM (in the horizontal (X) axis). Adding 1.5 kg (5.4 kg of total weight) to the weapon arrangement is possible with minor implications on user acceptance but configurations heavier than this (6.9 kg), are detrimental for acceptability of the surrogate models, and eventually the real weapons.

Limitations to study are related to features that are not included in the test bed design. The lack of recoil and the absence of a hand guard may be an important factor of poor acceptance among participants. Furthermore, a more realistic scenario should include some mobility and unexpected circumstances (like the appearance of a target). Also the simultaneous manipulation of weight and CoM can lead to a confound results.

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5 Conclusion

This study complemented the work done previously on weapon surrogates for the C7A2 regarding weights and CoM manipulation on the anterior/posterior (X) axis. Our findings confirmed suggestions made prior on appropriate weights used for this type of trial, and it is the first to explore the displacement of CoM in the vertical (Z) axis. Total weapon weights of 3.9 and 5.4 kg were qualified as “Acceptable” for participant in contrast to conditions with 6.9 kg that were judged as “Non-acceptable”.

Based on the findings from this experiment, future direction in the following area is therefore recommended: investigate the impact of soldier mobility on shooting performance when varying CoM in both the anterior/posterior (X) axis and the longitudinal (Y) axis for the 3.9 kg, 5.4 kg, and 6.9 kg conditions; investigate the effects of recoil; include a hand grip in the test bed; and manipulate CoM without simultaneously manipulating weapon weight.

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References

[1] Nakaza, E. T. and Tack, D. W. (2013). Future Small Arms Research (FSAR) Ergonomics Test Bed: Experimentation. Defence Research and Development Canada. In-press.

[2] Kelly, A. E., Tack, D. W., and Nakaza, E. T. (2013). Technical Memorandum – Future Small Arms Research (FSAR) Test Bed Development: Build Phase Summary. Defence Research and Development Canada. In press.

[3] Nakaza, E. T., Tack, D. W., Osborne A., and Zemsta, N. (2014). Future Small Arms Research (FSAR) Ergonomics Test Bed: Assessment of Weapon Load, Balance and Support on Simulated Marksmanship Task. Experimentation Report. Defence Research and Development Canada. In press.

[4] McKee, K. W. and Tack, D. W. (2009). Biomechanical Evaluation of Rifle Mass Properties Using Digital Modeling. Defence Research and Development Canada and the United States Marine Corps.

[5] Kleppner, D. and Kolenkow, R. (1973). An Introduction to Mechanics, (2nd ed.). McGraw-Hill, ISBN 0-07-035048-5.

[6] Spark Notes: Centre of mass at http://www.sparknotes.com/testprep/books/sat2/physics/chapter9section5.rhtml, (Access date: 21 April 2015).

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Annex A Study Information Sheet

Background: The FSAR program will support the Canadian Army’s (CA) next generation small arms project by developing a validated, science-based Statement of Operational Requirements (SOR) for a weapon system that will increase accuracy and lethality while at the same time be completely integrated into the soldier’s protective system. A prototype physical ergonomics test bed that consists of a set of aluminum channels that can be fitted with handgrips, magazine wells, NATO standard rail systems, weapon sights, and differing butt stocks. The test bed has a functional trigger that, when depressed, activates an electric solenoid to provide recoil. It is designed to accurately measure the effect of weapon size, weight, and balance on a soldier’s ability to aim and shoot. Weapon weight and balance can be adjusted using bolt-on weight plates of varying size and material composition.

Overview: A laboratory study will be undertaken at DRDC – Toronto Research Centre during the period of 12 January to 6 March 2015. Thirty (30) Canadian Armed Forces (CAF) personnel (male or female, aged 17 to 55) will be required to shoot a series of simulated serials using the test bed on a 3-metre instrumented firing lane located within a classroom or similar indoor facility. The test bed will be initially configured to simulate a C7A2 in size, weight, and center of mass. Using this test bed, the soldiers will first shoot two training applications. Each application will consist of a 5-round grouping, fired while in the standing position at an indoor facility. These two 5-round groupings are to familiarize the shooter with the size, shape, and weight of the test bed. After shooting each 5-round grouping, feedback will be provided to the shooter to improve accuracy with the test bed. Following this training application, the shooter will shoot two 5-round groupings, which will represent the test condition. The test bed weight, balance, and size will be systematically varied to the limits of design in the Z dimension. This will be done by manipulating the position of the bolt-on weights. For every change to the weapon center of balance and load support, the participant will shoot another two 5-round groupings. Data collected will consist of overall shot time, time between shots, grouping size, and point of impact (POI) accuracy relative to the center of the target and muzzle track relative to the center of the target. Every participant will have four sessions of half hour each during the week of his-her participation.

For participants run as part of the 2015 Winter Experimentation Campaign, the collection of demographics information and vision testing will be collected elsewhere (vision: 2014-044, Glaholt; demographics: 2013-065-Amendment 1, Tombu) and will be shared with the principal investigator of this protocol (Tombu). This is being done to reduce administrative burden on the participants and to streamline data collection

Your Rights as a Participant: Although you are filling a CFTPO position, your participation in this study is completely voluntary. You may ask questions of the researcher(s) at any time. You may end your participation at any time for any reason. If you decline to volunteer from the start, we will ask your unit to find a replacement volunteer. If you withdraw after starting the study, we will not use any of the data collected up to that point.

Confidentiality: The researcher(s) will take all steps to ensure that any data collected through your participation will remain completely anonymous, will be handled as confidential, and that no one will be able to identify you as a study participant in any presentations or publications made

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about the study. Participants will be given a unique identification number. This will be used in all studies. No other personal identifiers will be gathered. The demographic information will be used solely to describe the participant sample

Benefits: The benefit to the Canadian Armed Forces is further validation of a physical ergonomic test bed and understanding of the load forces affecting shooter performance and accuracy. The benefit to the participant is the development of an understanding of how weapon load forces affect shooter accuracy.

Risks: This protocol involves soldiers conducting a very benign, indoor firing exercise. There is no live firing. SCATT emits an eye-safe laser. This protocol is considered to be minimal risk. Risks include minor muscle aches and pains as a result of holding/manipulating the test bed and conducting turn-and-shoot exercises. This risk should not pose a problem for soldiers who are physically fit.

Contact Information: For any further questions or concerns about this project, or if you wish a copy of the final report, please contact Capt. Jose Peralta-Huertas, DRDC – Toronto Research Centre, 416-635-2330; 634-2330 (CSN); or [email protected]

This project has been reviewed and approved by the DRDC Human Research Ethics Committee (Protocol 2014-047). If you would like to speak with the Chair of this Board, please contact Dr. Don McCreary, 416-635-2098, or [email protected]

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Annex B Participant Information

PARTICIPANT INFORMATION Participant #:______

UNIT:

MILITARY  Junior NCM (Pte-MCpl) OCCUPATIO N:  Senior NCM (Sgt-MWO) (e.g. RANK CATEGORY:  Officer infantryman, 0311)

 Male GENDER:  Female

 African (non-Hispanic)  Asian  Caucasian (non- Hispanic) ETHNICITY:  Latino / Hispanic  Native American  Other: ______

 18-20  21-25  26-30  31-35  36-40 AGE:  41-45  46-50  51-55  56-60  60+

MARITAL  Married / Long-term  Separated / Widowed /  Never Married STATUS: Relationship Divorced

EDUCATION  High School  Bachelor’s Degree  Some College LEVEL: or below or higher

 Yes ALCOHOL USE CURRENT  No (drinks/day; 1 drink = 1  0  1  SMOKER: If yes, how many bottle of beer / glass of 2-3  4+ times per day? wine / shot of spirits): ______ Yes CHEWING  No  Never  Rarely TOBACCO VIDEO GAME PLAY: If yes, how many  Sometimes  Often USER: times per day? ______

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MARKSMANSHIP

WEAPON  Left shoulder  Left eye EYE DOMINANCE: SHOULDER:  Right shoulder  Right eye

 Yes, glasses  Left-handed CORRECTIVE LENSES HANDEDNESS:  Yes, contact lenses  Right-handed (for this tasking):  No

 PWT 1  PWT 2  PWT 3

MARKSMANSHI  PWT 3 Supplement (night Shoot)  PWT 4  PWT 4 P LEVEL: Supplement

LENGTH OF MILITARY SERVICE

YEARS IN  < 2 years YEARS IN RESERVES:  < 2 years REGULAR:  2-5 years  2-5 years  5-8 years  5-8 years  8-11 years  8-11 years  11+ years  11+ years DEPLOYMENT EXPERIENCE Please note operational experience by theatre, year and tour duration (e.g. Afghanistan, 2006, 12 months)

ENGAGEMENTS

Were you involved in any  Yes live-fire engagements while  No on operations? Indicate the number of live- fire engagements you have  1-4  5-10  11-20  21-35  35+ experienced while on operations:

26 DRDC-RDDC-2016-R176

COMBAT EXPERIENCE Please detail any combat experience where you have used your weapon. Estimate the ranges of engagements, type of fire (aimed, suppressive, etc.), effects of fire, day vs night missions, etc., and break down each type as a percentage of total engagements.

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Annex C Configurations

Figure C.1: N configuration.

Figure C.2: 1.5A configuration.

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Figure C.3: 3A configuration.

Figure C.4: 3B configuration.

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Annex D User Acceptance Questionnaire

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32 DRDC-RDDC-2016-R176

List of Symbols/Abbreviations/Acronyms/Initialisms

ANOVA Analysis of Variance CAF Canadian Armed Forces CFTPO Canadian Forces Task Planning and Operations CoM Centre of Mass CTS CADPAT Clothe the Soldier Canadian Disruptive Pattern DRDC Defence Research and Development Canada FFO Full Fighting Order FPV Fragmentation Protective Vest FSAR Future Small Arms Research HF Human Factors HREC Human Research Committee NATO North Atlantic Treaty Organisation POI Point of Impact PWT Personnel Weapon Test RCR Royal Canadian Regiment SOR Statement of Operational Requirements WBE Work Breakdown Element

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DOCUMENT CONTROL DATA (Security markings for the title, abstract and indexing annotation must be entered when the document is Classified or Designated) 1. ORIGINATOR (The name and address of the organization preparing the document. 2a. SECURITY MARKING Organizations for whom the document was prepared, e.g., Centre sponsoring a (Overall security marking of the document including contractor’s report, or tasking agency, are entered in Section 8.) special supplemental markings if applicable.)

DRDC – Toronto Research Centre UNCLASSIFIED Defence Research and Development Canada 1133 Sheppard Avenue West 2b. CONTROLLED GOODS P.O. Box 2000 (NON-CONTROLLED GOODS) Toronto, Ontario M3M 3B9 DMC A Canada REVIEW: GCEC DECEMBER 2011

3. TITLE (The complete document title as indicated on the title page. Its classification should be indicated by the ap propriate abbreviation (S, C or U) in parentheses after the title.)

Future Small Arms Requirements WBE 2.4 Load Balance and Support in Weapon Design: Manipulation of Weapon Weight and Centre of Mass About the Vertical (Z) Axis

4. AUTHORS (last name, followed by initials – ranks, titles, etc., not to be used)

Peralta-Huertas, J.; Natale, A.; Honey, J.

5. DATE OF PUBLICATION 6a. NO. OF PAGES 6b. NO. OF REFS (Month and year of publication of document.) (Total containing information, (Total cited in document.) including Annexes, Appendices, etc.) August 2016 44 6

7. DESCRIPTIVE NOTES (The category of the document, e.g., technical report, technical note or memorandum. If appropriate, enter the type of report, e.g., interim, progress, summary, annual or final. Give the inclusive dates when a specific reporting period is covered.)

Scientific Report

8. SPONSORING ACTIVITY (The name of the department project office or laboratory sponsoring the research and development – include address.)

DRDC – Toronto Research Centre Defence Research and Development Canada 1133 Sheppard Avenue West P.O. Box 2000 Toronto, Ontario M3M 3B9 Canada

9a. PROJECT OR GRANT NO. (If appropriate, the applicable research 9b. CONTRACT NO. (If appropriate, the applicable number under and development project or grant number under which the document which the document was written.) was written. Please specify whether project or grant.)

10a. ORIGINATOR’S DOCUMENT NUMBER (The official document 10b. OTHER DOCUMENT NO(s). (Any other numbers which may be number by which the document is identified by the originating assigned this document either by the originator or by the sponsor.) activity. This number must be unique to this document.)

DRDC-RDDC-2016-R176

11. DOCUMENT AVAILABILITY (Any limitations on further dissemination of the document, other than those imposed by security classification.)

Unlimited

12. DOCUMENT ANNOUNCEMENT (Any limitation to the bibliographic announcement of this document. This will normally correspond to the Document Availability (11). However, where further distribution (beyond the audience specified in (11) is possible, a wider announcement audience may be selected.))

Unlimited

13. ABSTRACT (A brief and factual summary of the document. It may also appear elsewhere in the body of the document itself. It is highly d esirable that the abstract of classified documents be unclassified. Each paragraph of the abstract shall begin with an indication of the securi ty classification of the information in the paragraph (unless the document itself is unclassified) represented as (S), (C), (R), or (U). It is not necessary to include here abstracts in both official languages unless the text is bilingual.) A laboratory study was undertaken at Defence Research and Development Canada – Toronto Research Centre (DRDC – Toronto Research Centre) during the period of 12 January to 6 March 2015. Thirty two (32) Canadian Armed Forces (CAF) personnel (male, aged 21 to 40) were asked to shoot a number of simulated serials using the surrogate test bed on an instrumented 8-metre-wide indoor firing lane. The test bed was initially configured to simulate a C7A2 in size, weight, and centre of mass (CoM). The test bed weight, and balance were varied systematically resulting in four configurations as follows: N: same weight as C7A2, CoM at the same location as C7’s; 1.5A: 1.5 kg heavier that N configuration, CoM above C7’s (about 5 cm); 3A: 3 kg heavier that N configuration, CoM above C7’s (about 5 cm); and 3B: 3 kg heavier than N configuration, CoM below C7’s (about 2 cm). This was done by manipulating the position of the bolt-on weights along the vertical (Z) axis through the theoretical CoM. The CoM was manipulated along the local coordinate system of the weapon. For every change to the weapon’s center of balance and weight, the participants shoots two 5-round groupings. Data collected consisted of 6 marksmanship metrics collected using the SCATT software that is a simulated marksmanship system. A significant difference was found in only one measure, the Mean Group Centre Radius, during the standing hold serial. This measure for N condition was significantly smaller than the one for 3A condition (p = .04). In contrast, all heavy configurations (1.5A, 3A and 3B) failed in Overall (Weight, Balance and Acceptance) factors according to participants. These findings may indicate that weight and CoM manipulations on vertical (Z) axis have minimal effect on marksmanship in spite of poor acceptance among shooters.

14. KEYWORDS, DESCRIPTORS or IDENTIFIERS (Technically meaningful terms or short phrases that characterize a document and could be helpful in cataloguing the document. They should be selected so that no security classification is required. Identifiers, such as equ ipment model designation, trade name, military project code name, geographic location may also be included. If possible keywords should be selected from a published thesaurus, e.g., Thesaurus of Engineering and Scientific Terms (TEST) and that thesaurus identified. If it is not possible to select indexing terms which are Unclassified, the classification of each should be indicated as with the title.)

Weapon; load balance; centre of mass.