In order to participate in the GunBroker Member forums, you must be logged in with your GunBroker.com account. Click the sign-in button at the top right of the forums page to get connected.
.308 brass with military headstamp question..
SwanKong
Member Posts: 989 ✭✭✭✭
I have 50 .308 brass with a the headstamp RA 64. My question is can I load this the same as I would brass stamped with .308 Win.? Does it have thicker case walls therefore a different case capacity?, which would mean different data?..
Comments
You will also have to remove the crimp left after decapping the spent primer.
The old Win SuperSpeed was thinner brass (one of my fav's). Full case loads of slow powder were sort of self adgusting, less than full case with faster powder can cause problems.
All the data I ever see lists every componet: case, powder, primer bullet OAL etc for a reason. Always wise to back off some if you change things
The simple answer is to fill one of those cases with water and weigh it. Weigh an empty case and subtract. Do the same with a commercial case and compare.
You can also section one of these and a commercial case which will allow you to measure the variations in case wall thickness.
Best.
Even switching to European made brass may result in significant pressure variances. I found that a starting load listed for domestic 8x57 brass gave flattened primers and max load velocity when loaded in xyz brand(made in eastern Europe)brass.
ALWAYS err on the side of safety and work up.
Reduce the "pet" load by 5% using all your old components. Fire and chronograph. (You'll get a bit less speed due to the reduced pressure.)
Now shoot that same 5% reduced load in the new brass (NO other component changes!) and chrono it.
If the velocity is the same with both old and new brass, you can go back to your favorite load with no other testing required.
If the velocity is LOWER with the new brass, you can work up to the original velocity level.
If the velocity is HIGHER with the new brass - but lower than your original "pet" load got - you can work up to the original.
If the velocity is HIGHER than even the original "pet" load, you have a serious problem with the new brass. Consider tossing it. But at least you only wasted a few shots worth of components.
You can also add water and weigh, then add water to a standard brass case and weigh and compare the percentage difference. Military brass is usually lots heavier than standard brass when weighed on a scale, the brass walls are thciker and LESS volume inside, therefore same amount of powder in a military case as compared to a standard brass case will produce more pressure/velocity therefore reduce the power charge by the percentage difference.
When I have military brass and a very accurate rifle I first work up a accuracy load with standard brass, then later I separate the military brass by weight into about 10% weight piles, then take the majority that are close to same weight, with-in 5 grains then start testing for accuracy using the 10% reduced powder charge and watching the velocity thru a chronopgraph and the on target results.
I usually end up using the military brass labeled as practice/scope setting rounds, separated from my mail hunting brass.
If a gun is real touchy for accuracy vs a powder charge, mixing military brass and standard brass can make a very good accurate shooting rifle look real bad on paper for accuracy point of impact! I've seen groups shift by as much as 3 inchs at 100 yards mixing military brass and standard brass with the same powder charge. (not paying attention to the volume/charge of powder reduction or separating the brass per weight)
There is a considerable difference between 308 NATO ammo fired in machine guns and semi auto rifles. The machine gun chambers are rather huge compared to rifle chambers. They are difficult to size and will only last a couple of loadings.
I did not know that about the huge chambers!!!!! I ran into some of the military brass that was very hard to re-size and suspected been fired oversized chambers!
While the external dimensions are the same, the NATO was loaded for lower pressures that the .308, AND military brass is thicker. This means the internal volume of a case is less. Use civilian .308 load data in a NATO case, your pressures are going to be higher than expected.
As the man said, back off the starting load by 10%.
NRA's Formula for reloading Military Brass. Weigh the Military Brass. Then weigh the Comercial Brass. Commercial Brass is thinner so it weighs less. Subtract the weight of the commercial brass from the Military Brass. Multiply the result by 12 percent. this is the amount you reduce your load by.
example:
Military case weighs 184 Grains
Commercial case weighs 175 grains.
184 - 175 = 9
9 X .12 = 1.08 grains.
Reduce your load by 1.08 grains.