Riflescopes and You

By 2009 Individual Marksmanship Training LLC

This article is not meant to be a brand sales pitch or a write up of what is best to buy for the money. Rather, it is a short piece on what the difference is within the current market, how to pick the best riflescope for your use and how to spend your money as wisely as possible.

People send me a lot of e-mails, messages etc. across many different forums over the years asking me what riflescope I should get for XYZ rifle. I always reply with a pasting of a long list of questions that I have typed up in a MS Word document that I reply back with. This is a breakdown of that list and a deeper explanation of each part.

Different options and details explained:

Minute of Angle MOA 1 that is, for the arcminute. This unit is commonly used in target shooting to express the angular size of targets or the spacing between marks on a reticle (the grid of lines seen in the eyepiece of a rifle). By coincidence, 1 moa is very nearly equal to a target size of 1 inch at 100 yards; in fact, 1 moa = 1.04720 inches at 100 yards or 10.4720 inches at 1000 yards. In metric units, 1 moa = 2.9089 centimeters at 100 meters.

Inch Per-Hundred Yards IPHY “Shooter MOA” is a term used to explain American style adjusted scopes that will move the reticle 1 inch at 100yds or 2.42 centimeters at 100 meters per-1 “IPHY” adjustment made to the optic. IPHY has the same four standards of click values as MOA.

Metric adjustment is the same value as milliradian “MILRAD” adjusted riflescopes; the only difference is in the labeling of the knobs and literature that came in the riflescope box.

Milliradian “MILRAD” A unit of angle measure equal to 0.001 radian. The milliradian equals about 0.057 296°, 3.43775 arcminutes, or 3" 26.265'. In Britain this unit is often called the angular mil. MILRAD adjusted scope is a true milliradian based adjustment. The two most popular click values are 1/10th and 2/10th milliradian adjustment, this gives a shooter an optic that adjusts in the same value as their Mil- Dot reticle. The 1/10th or 2/10th value is based on the unit of measure used for the targets distance. If you measure your targets distance in Metric, your click value is 1/10th or 2/10th of a meter at each 100m line. The same situation for the English unit of measurement of yards, the click value is 1/10th or 2/10th of a yard at each 100yd line.

Parallax2 is the apparent movement of objects within the field of view in relation to the reticle.

Field of View3 “FOV” Field-Of-View Essentially, how much of the targeted area that is visible when viewed through the scope. This measurement may be given either in linear or angular measurement. The measurement is normally taken across the diameter of a circular field and, in the U.S., expressed for scope sights, in feet or yards at a subject distance of 100 yards unless otherwise stated. The field-of-view of binoculars is generally given for 100 or 1,000 yards. In countries using the metric system, field-of-view is commonly expressed in meters at a subject distance of 100 or 1,000 meters.

© 2009 Individual Marksmanship Training LLC Objective Size is measured in millimeters in diameter. A larger objective lens allows more light to enter the scope. In a three and a half to ten by forty-four (3.5-10X44) scope, the 44 is the objective lens size. This measurement does not include the housing built around the objective lens. exit pupil4 is a virtual aperture in an optical system. Only rays which pass through this virtual aperture can exit the system. The exit pupil is the image of the aperture stop in the optics that follow it. In a telescope or compound microscope, this image is the image of the objective element(s) as produced by the eyepiece. 1 http://www.unc.edu/~rowlett/units/dictM.html

2 http://www.usoptics.com/parallax.php5 Eye relief3 http://www2.leupold.com/resources/MyInfo81/Answerbook/findanswers.aspxof a telescope, a microscope, or binoculars is the distance from the last surface of an eyepiece at which4 http://en.wikipedia.org/wiki/Exit_pupil the eye can be placed to match the eyepiece exit pupil to the eye's entrance pupil.

Tube Size is the outside diameter of the material the riflescopes body measures for mounting options. A larger tube size does not equal greater clarity or crispness of images in the riflescope or a stronger tube than a smaller outside diameter. But the tube size is an indication of a higher amount of ballistic adjustment.

How do I check all this information on my riflescope? Most of the above information is easy to check and see what you have, the simplest steps is to read the literature that came in the riflescope box. To do a more in-depth check or to burn up your weekends testing your equipment you need to have some simple computer programs and some normal household items. I am going to walk you through how I check my own rifle scopes.

Riflescope adjustment values:

I use MS Office Power Point to make testing scales for my adjustment values. Since we now understand there are two types of MOA be it, true MOA and IPHY; but there is only one kind of MILRAD. I make a group of testing targets that fit these known adjustment measurements. Let’s talk about making a simple MOA and IPHY adjustment scale sheet. On three standard pieces of paper I make two lines that are spaced at a known inch value away from a 1 inch target dot. One line value in MOA and the other line value in IPHY for all three pieces of paper.

I use the following distance between the center of the target dot to value lines to get my riflescope‘s unit of measure.

Page 1.

• 4.75 inches • 5.00 inches

Page 2

• 5.75 inches • 6.00 inches

• 7.75 inches • 8.00 inches

The deal is this, on all test pages I set them up at 100yds to the nose. Then place the reticle on the 1” target dot dead center mass. For page one I adjust the optic 4.75 or 38 clicks worth of total elevation. If the riflescope in IPHY the reticle will be on the 4.75” line, if the riflescope is on MOA it will fall on the 5.00” line. It’s that simple so for the other two sheets the same thing. Take the first distance and that is your adjustment value from the target dot to see where the reticle lands at.

MILRAD checking is very simple, take two yard sticks and make a cross at the 18” line put two screws in them to hold it together. Use a carpenter’s triangle to get 90 deg to each other. At 100yds, level the 36”x36” cross and go back to your testing line. Adjust the elevation line 5 MILRAD you will move the reticle 18”. IF you go 2.5 MILRAD that’s 9” of movement, keep in mind a Mil is 3.6” in diameter at 100yds so you can do the math here, its 10 th of a yard(??) . Then with the reticle you can see the 36” equals 10 mils. Have fun, MILRAD is so easy. 5 http://en.wikipedia.org/wiki/Eye_relief Parallax is very easy to check, most riflescopes come with a parallax adjuster of some type, like a side knob or an adjustable objective. Optics that do not have adjustable parallax are typically set for 100yds in the United States. To check your parallax setting is simple. Lock up the rifle in what ever shooting position you are in, raise your head off the comb and move your head in a circular manner. If the target dances around the Point of Aim (“POA”) than adjust your parallax.

If you have a non-adjustable parallax riflescope, you need to know what a proper cheek to stock weld is. You must have your eye line up with the scope’s axis the same way EVERY time you shoot to minimize parallax. One way to help you on a non-parallax riflescope is to buy a brand that has a custom shop that will adjust the parallax setting. Like Leupold or US Optics. I have my parallax adjusted from 100yds to 300yds. This gives a maximum parallax error of 2 MOA at 1000yds in my testing.

Field of View is listed at manufactures websites or in the literature that came in the riflescope box. But these numbers are the standard for that model of riflescope. That does not always ring true when the riflescope is in your hands. How to check this is simple when assisted with a friend. All you need is a field, some landscaping flags, measuring tape and the riflescope being tested in a steady mount.

In an open field mark off 10yds, send your buddy to the designated yard line and take some landscaping flags. Adjust your riflescope to its lowest magnification setting and have your buddy at the 9 o’clock position to the riflescope a few yards out of the line of sight. IF you can see him in the riflescope have your partner back up more.

Now, your partner walks in a line that keeps the same distance from the testing site trying to stay parallel of your position. As soon as you see him in the left edge of the rifle scope tell him to STOP and place the first flag. Now you adjust the magnification ring to its highest setting, and ask your buddy to start walking again. Once you see him, your buddy STOPS and sets the second flag. Have you buddy continue to walk on by until he passes the right limit of the riflescope. He backs up and places the third

Now you have to measure the distance from flag one and flag four to get the low end FOV, and the distance from flag two to flag three for high end FOV. IF you do this at 10yds, multiply the distance by ten to get the FOV at 100yds or what ever multiplier you want to use to get the FOV at that distance.

Eye relief does vary between different riflescopes, firing position to firing position and from shooter to shooter based upon:

• The shooters neck length.

• Your angle of head approach to the stock.

• The depth of your shoulder pocket.

• The position of the butt of the stock in the shoulder.

• Your firing position.

This distance is more rigidly controlled with telescopic sights than with iron sights. The shooter must take care to prevent eye injury caused by the rear sight or the telescope tube striking your eyebrow during recoil. Regardless of the sighting system you use, the key is to place your head as upright as possible with your firing eye located directly behind the rear portion of the sighting system. This head placement also allows the muscles surrounding your eye to relax. Incorrect head placement causes the shooter to look out of the top or corner of your eye, which can result in blurred vision or eyestrain. You can avoid eyestrain by not staring through the iron or telescopic sights for extended periods.

The best aid to consistent eye relief is maintaining the same stock weld from shot to shot; because as the eye relief changes, a change in sight alignment will occur. Maintaining eye relief is a function of the position and stock weld use.

Ok so the next question of the new year is this, how does all this help me?

Well it educates you on picking the right tool for the job at hand. Picking an $800 riflescope that does not do what you need it to is a major letdown. I have students arrive at a class equipped with a $2500 riflescopes that failed to suit their needs. I want you to be able to say, I need a riflescope that has a FOV of 18 ft @ 50yds, eye relief of 3.5 inches, true MOA adjustment that tracks right, and a reticle that works for XYZ shooting. Once your needs are figured out, you can go buy a riflescope to fit your needs and budget which should result in you being happy!

There is a ton of optics on the market today. My personal picks are slim to say the least. I pick my riflescopes to match the rifles design. I am the type of person likes to design a rifle, riflescope, mounting, caliber to fill a specific need even if that need is a “do all rifle”. When I picked the Horus 3-12x50mm Hawk for my 18” CLE SPR AR-15, I did that because of the type of shooting I will do with that rifle. All

When I designed the A5 reticle for the IOR 3-18x42mm First Focal plane riflescope, I had passive mil ranging of targets in mind down to the .05mil, hold-overs to 900yds if needed, and the ability to see the reticle at 3x magnification.

Your needs might be different than mine, if you hunt whitetail in the southeastern United States, I would tell you to run a point blank zero for a eight inch target and a reticle that will let you do so no matter the outside brightness of sunlight. My optic of choice to fit these needs is the Trijicon Accu-Point TR21-3, due to the wide FOV, Eye relief and the reticle is in the 2nd focal plane. At 1.25x magnification the illumined part of the reticle is 2.4 MOA and at 4x magnification the illumined part reticle is .9 MOA. No batteries to go dead, and works in daylight or nighttime. Also since most of your shots are under 300yds, you do not need a 12-42x56mm rifle scope. You needs a light weight do all riflescope.

The “Old School” rules of thumb still apply today as well as they did back then. In the 40’s a rule came out that you need 1x magnification per 100yds of targets distance. If you think about it, this makes a lot of since. Many long range matches have been won at 1000yds with a fixed 10x scope, many of Africa’s wild game have been killed with a fixed 4x riflescope. Look no deeper than the Trijicon ACOG 3.5x or 4x the U.S. Military uses to gain kill shots to 600yds or more.

I hope this long winded write up will aid you in selecting the right tool for the job. I am by no means an expert, just a person with some experience wishes to share his thoughts on the matter.

John Boyette

Individual Marksmanship Training LLC.

Training Director