Military Brass - Charge Reduction

[Martyk]

When reloading military brass, I read somewhere that the charge should be reduced by 1 (or so) grain.

Anyone have any comment on this? Is this common practice? If so what is the reasoning?

Thanks,

 

[Bartkowski]

I haven't read it anywhere, but it wouldn't hurt. The reasoning behind it is probably because military 5.56 brass is usually thicker than commercial .223 (or any other cartridge that has a commercial and military "version" of the case). That could cause the pressure to be higher.

I always figured that it would be safe to back off a grain, but rarely use military brass so I don't if it is neccessary.

 

[rcmodel]

7.62 & 30-06 GI brass has greatly reduced case volume due to much heavier & thicker brass.

Not so much with 5.56mm.

Some of it is slightly heavier then commercial .223 brass.
But some of it is lighter.

Just start with a listed starting load, and work up as you always should anyway.

rc

 

[Mark whiz]

With 30 caliber mil-spec brass - the old NRA standard is to reduce the powder charge by 15% when converting a load in commercial cases to military cases.
If you have the scale and time - you can weigh both sets of cases, average the result, and change your load by the same percentage between the cases. But I have found the 15% rule works real well.

 

[USSR]

With 7.62x51 brass, reduce your charge weight by 1.5-2.0gr, as there is a big difference in case capacity between it and almost all commercial .308 brass. This is not always the case with 5.56 and .30-06 brass, infact Lapua and Lake City Match brass in .30-06 have essentially the same case capacity, and loads are interchangeable between them.

Don

 

[Martyk]

Thanks for the info so far. I AM referring to 7.62 x 51. So the thicker case results in a lower internal case volume.. huh. I thought I had heard this but wanted to confirm.

 

[fguffey]

Martyk, now you have all of the standard answers, before you say "oh, now I understand" let me add this, it always starts with military brass is heavier because it is thicker, that is half truth, the military case web is thinner, the web on 30/06, 1940 to 1960+ is .200 + or - a few, commercial brass we have measured is .260 +, so the web on the military brass I have measured is .060 thinner than commercial brass, THICKER BRASS, If the web is thinner at the web and weighs more, the body of the case must be thicker, if the body of the case is thicker, and the outside diameter stays the same, the column of powder inside the military case is longer and smaller in diameter than the columns of powder inside the commercial case, and, cases that weigh the same does not mean the column of powder is the same, cases can weigh the same, thin web/thick body or thick web/thin body.

Military brass is heavier with exceptions, WCC, WRA and WW military case are straight across lighter than military cases in 30/06.

Is difference a difference? When comparing cases use the depth end of the dial caliper to measure the inside distance from the mouth of the case to the web (record) then measure the case length (record), subtract the depth from the length to get web thickness, cases that weigh the same does not mean they are the same.

I have read claims case protrusion on military 30/06 bolt guns can be as much as .170, if one thinks about it when using military brass, there is only .030 of the web that is supported, I have never found an 03 or M1917 with more than .090 protrusion, Mausers, without measuring .110 - or + a very few. I have found 303 British cases with a web that measured .130, even though the 303 could be considered a 100% case supported cartridge, I would not use the 303 cases with the thin web.

F. Guffey

 

[Martyk]

Hey Guff - thank you for the detailed response. Good info to think about. You may have given me a clue to a few other things I've been pondering.