Reloading Imperial Japanese Rifle Cartridges Part II – Reloading 7.7Mm Japanese (Updated 13 September 2009) Shannon M

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Reloading Imperial Japanese Rifle Cartridges Part II – Reloading 7.7mm Japanese (Updated 13 September 2009) Shannon M. Zeigler

Author’s Note: This is a special edition of my second revision of an article originally published in Banzai, The Japanese Militaria Collector’s Bulletin,2003 Issue 230, pp 127-30. The article is divided into two parts. Part I Reloading the Japanese 6.5x50mm Semi-Rimmed (SR) Cartridge and Part II Reloading the 7.7x58mm Cartridge.

This author assumes the reader has a basic knowledge of reloading. There are numerous reloading manuals and websites that can address the more detailed aspects of reloading. I assume no liability and strongly encourage users to reference current reloading publications, and practice all basic reloading safety. I feel safe using these methods, but as I say, “your loads, your life, your choice”.

7.7mm Japanese (7.7 X 58mm Rimless). Reloading the 7.7mm cartridge provides reloaders with numerous options in both brass and bullets. Norma, P.C.I., and Hornady offer factory 7.7mm ammunition from $17.99 to $35.99 for a 20 round box1. 100 unprimed cases list for $41.99 for PPU and $109.20 for Norma. Once-fired .30-06 and 8x57mm Mauser offers an alternative to buying factory cases.

7.7mm formed from .30-06 (.30 caliber). .30-06 cases are a readily available source for making 7.7mm. Finding once-fired .30-06 is fairly easy, and relatively inexpensive to buy. However, it is time consuming to reform. The primarily problem is length. .30-06 brass is nominally 2.485 inches (63mm) long versus 7.7mm which is 2.285 inches (58mm) in length. The additional length makes it necessary to trim approximately ¼ inch (5mm) after initial sizing. Using a form and trim die is the best method to efficiently make the initial case form and remove the excess brass. The form and trim die is simple to use. Lightly lube the case, size and then cut the excess brass protruding from the die with a hacksaw. As an aside, Imperial die wax is an outstanding (I submit the best) lubricant to use for case forming. Using the form and trim is worth the extra effort and saves time during the final trim-to-length step. If you don’t use a form and trim die, a powered case trimmer is a must to remove the excess case length. A manual trimmer is too tiring and time consuming. I use Redding’s form and trim die - $43.39 from Graf and Sons. It is high quality and easy to use. Use of the form and trim die does require final trim-to-length and case mouth deburring. Sierra recommends a trim-to-length of 2.260 inches and an overall maximum length of 3.150 inches. Some reloaders and manuals consider reformed .30-06 unsafe because the case head diameter is too small. I disagree. According to Sierra, 7.7mm has a case head diameter of .471 inch compared to .30-06 diameter of .470 inch. I think the difference is negligible. I have measured original 7.7mm case heads and have found some to measure .470 inch as well. We are reloading for bolt action military rifles with greater tolerances than found in commercial firearms. Annealing and close inspection of fired cases will reduce the chance of case head separation. A standard USGI .30 cal broken shell extractor will remove a case if you should experience separation. Annealing is beyond the scope of this article. In the bibliography I have included a link to Ken Light’s excellent article on annealing. Many well written articles on annealing can be found on the internet using a good search engine.

7.7mm formed from 8mm Mauser (8mm X 57mm). I primarily use .30-06 brass to make 7.7mm because of availability, but I prefer to reform 8mm Mauser. Boxer primed surplus and commercial once fired 8mm is not as readily available as .30-06, but you can buy new PPU 8mm starting at $39.99 per one hundred. To reform 8mm into 7.7mm simply lube the case and resize in a 7.7mm sizer die. It is that simple and easy. 8mm Mauser is one millimeter shorter than 7.7mm Japanese

1 Refer to Table 1. so there is no need to trim-to-length. The Sierra reloading manual gives the 8mm a case head diameter of .469 inch versus the 7.7mm’s .471 inch a difference of .002 inches, negligible in my opinion. Quality brass, careful case inspection, and annealing will reduce the chance of case separation.

Another 7.7mm source is berdan primed 8mm military surplus ammunition. Using surplus 8mm is fairly straightforward. First remove (pull) the bullet, dump the powder, neck size the case without the decapping pin installed, replace the correct powder charge, then replace the .323 inch bullet with a similar or lighter weight .311 inch bullet. Depending on the source ammo, it may be necessary to completely discard the original powder or reduce the original charge to safe levels. It is a matter of safe practice to reduce the original charge by 10% and work up to a satisfactory load. Most military surplus 8mm is corrosive and appropriate care must be taken when cleaning your bore.

7.7mm Rifle Specifications. Original Japanese ball ammunition has a 184 grain flat base FMJ bullet with an average velocity of 2400 fps. I pulled an original Type 99 Rifle bullet and found it to be loaded with 42.3 grains of square flake power with a .3105 inch diameter, 181.3 grain flat base FMJ bullet. Like the Type 38, the Type 99 Short Rifle is known to have larger diameters than specified – up to .316 in my experience. The Type 99 Light Machine Gun round had a slightly longer ogive and was loaded with a 203 grain bullet. Table 3 lists bore and groove diameters from Mike Rockhill’s and my collection. We each slugged a Type 99 Jinsen barrel and found the bores to be remarkably consistent along the length of the bore. Whereas I noticed that my Toyo Kogyo and Nagoya bores were tighter near the chamber, but opened up as I pushed the slug (lead fishing weight) along its length.

7.7mm Rifle Loads. The 7.7mm offers handloaders numerous bullet and powder options. Hornady, Sierra and Speer offer bullets in the 123 to 180 grain range suitable for the Type 99. Additionally, 7.65 Argentine, .303 British, 7.62 x 54R (7.62R) Russian and 7.62 x 39mm all use .310 to .311 diameter bullets, and are a good bullet source. The best source is 7.62R. Prices for surplus 7.62R ammunition have doubled since I first wrote this article, but you can buy a 440 round tin for $79.99 plus shipping. Surplus 7.62R is a less expensive source of bullets and powder. While not as cheap as a 440 tin of 7.62R at $39.99, it is still less than factory ammo, especially Norma cartridges. You can harvest up to 3 ½ pounds of powder from the cartridges. The powder value alone is almost worth the expense, if you re-use the powder reduce the original charge by 10% and work up. I have found the quality and accuracy of surplus COMBLOC bullets and powder acceptable for the Type 99. As a last option you can use .308 inch diameter bullets. I have not experienced a noticeable difference in plinking accuracy at short distances, however beyond 50 to 100 yards accuracy falls considerably. I prefer IMR 4895 and 4064 when I load for 7.7mm. I load 45 grains of IMR 4895 behind a 150 grain bullets and 42 grains when loading the 174 grain bullets. All loads are on the conservative side and accuracy varies between guns, but I have found them to be acceptable in most Type 99 rifles. Refer to table 3. for load data.

Conclusion. Again, I am grateful to Frank Allan and Mike Rockhill for their comments and assistance with writing this article - Thanks. Please send questions or comments to my email listed below. Table 1. Component and Ammunition Cost: www.grafs.com/ 17 December 2008 Caliber Make P.C.I. Hornady Norma Prvi Partizan 7.7mm Ammo per box 20 rounds $17.99 $23.99 $35.99 Unprimed Cases per 100 109.20 41.99 Bullets per 100 Prices range on average from $7.50 (pulled surplus) to $27.00 per 100

Table 2. 7.7mm Bore Diameters Samples Rifle/ Serial Bore Groove Arsenal Series Remarks Carbine Number Diameter Diameter Type 99 TJK 37 51705 .301 .313 Type 99 Jinsen 40 78121 .302 .311 consistently tight bore Type 99 Kokura 21 60777 .302 .3145 .312 Hdy SP shot well Type 99 Toyo Kogyo 30 32249 .3025 .314 Type 99 Nagoya 4 23134 .3025 .315 not as tight toward muzzle Type 99 Jinsen 40 50906 .3025 .316 consistently tight bore Table 3. Select 7.7mm Reloading Data

Bullet Bullet Average Extreme Standard Shots in Rifle Powder Charge Weight Type Velocity Spread Deviation String Remarks S:21 SR SR 4795 20.0 123 SP 1549 101 33.9 10 Squib Load - very mild recoil S:21 SR IMR 4064 40.0 147 FMJBT 2270 171 54.0 10 Suplus 7.62R bullet S:4 SR AA 2230-C 46.0 150 FMJBT 2547 89 35.0 5 AA 2230-C is similar to A 2230 S:4 SR AA 2230-C 45.0 150 FMJBT 2557 97 42.1 5 AA 2230-C is similar to A 2230 S:4 SR CZ 41.8 150 FMJBT 2414 98 39.0 9 1960's Czech Silver Tip & Powder S:4 SR CZ 42.9 150 FMJBT 2501 243 72.0 9 1960's Czech Silver Tip & Powder S:4 SR CZ 44.5 150 FMJBT 2593 103 33.0 10 1960's Czech Silver Tip & Powder S:21 SR IMR 3031 40 150 SP 2377 164.7 52.12 9 1 x not recorded S:4 SR IMR 4064 45.7 150 FMJBT 2668 104 40.0 5 Czech Silver Tip .3105 dia S:4 SR IMR 4895 42.0 174 FMJBT 2213 123 50.5 5 Suplus IMR powder S:4 SR IMR 4895 43.0 174 FMJBT 2405 157 58.7 5 ≈ Mil Spec Suplus IMR powder S:4 SR IMR 4064 45.7 180 SP 2466 33 15.0 5 S:4 SR 1950's Hun. 42.0 184 FMJBT 2207 152 46.0 9 Surplus Hungarian Yellow Tip S:4 SR 1950's Hun. 43.0 184 FMJBT 2277 102 39.0 8 Surplus Hungarian Yellow Tip S:4 SR 1950's Hun. 44.0 184 FMJBT 2290 101 33.0 9 Surplus Hungarian Yellow Tip S:4 SR 1950's Hun. 44.5 184 FMJBT 2352 105 29.9 10 Surplus Hungarian Yellow Tip S:4 SR 1950's Hun. 45.0 184 FMJBT 2371 96 27.0 10 Surplus Hungarian Yellow Tip S:21 SR 4320 40.5 185 FMJBT 2115 220.8 77.6 10 Pulled Argentine bullets - reformed 8mm

S:21 SR IMR 4320 42.6 185 FMJBT 2190 237.8 72.7 10 Pulled Argentine bullets - reformed .30-06 S:21 SR Factory 203 FMJ 2327 58 19.2 9 Original IJA - one primer failed to fire

Bibliography:

Allan, Frank and Macy, Harold. The Type 38 Arisaka. Palm Coast: Francis C. Allan, 2007.

Graf & Sons website, http://www.grafs.com/, 17 December 2008.

Gunboards.com website, www.gunboards.com, 30 December 2008.

Los Angeles Silhouette Club website, Cartridge Case Annealing with the BC-1000 Annealer When, why, how and if to anneal By Ken Light http://www.lasc.us/CartridgeCaseAnnealing.htm, 17 August 2009.