View Full Version : 'NATO Spec' Ammunition? (a treatise)
June 02, 2001, 18:13
The Myth of 7.62x51mm NATO interchangeability (http://www.cruffler.com/trivia-June01.html)
Food for thought
[ August 10, 2001: Message edited by: EMDII ]
June 02, 2001, 20:09
It was a very interesting piece with lots of good info. The only point I question in my brief perusal is the assumption that all NATO countries use IMR 4895 as their propellant. The variation in charge weights is then assumed to give varying performance. Am I off base?
June 02, 2001, 20:21
I don't have the documentation to support or refute a claim of universal IMR use. However, it is possible, and highly probable that uniformity STANAG (the 4-leaf clover) ammunition would be fabricated using a standard propellant.
FWIW: 120mm STANAG tank ammunition IS identical, even down to primer and powder specs.
June 03, 2001, 00:59
All countries don't use 4895.
The 4895 reference in the Cruffler article was only to demonstrate the difference in long-range point of impact between fairly small differences in powder-charge weight. The 4895 is just a hypothetical example. The Cruffler didn't intend to imply that any country (even the US for that matter) uses a powder we can put our finger on.
Ammo companies typically blend different types of powder to achieve a particular burn rate for large lots of ammunition. The powder in this year's run of military rifle powder may be a different blend than last year. But, the burn rate will be consistent. The burn rate is the "milspec" that gets tested. Smaller lots sold to handloaders are not blends. That is why you will find some alarming differences from year-to-year in the pressures you get from a particular "commercial" powder. That is also why many manufacturers list conservative data as their published "maximum" load.
The problem with the military ammo manufacturers is that they are sloppy about how they meter their powder charges, and that sloppiness was essentially the point of the Cruffler article.
June 03, 2001, 06:42
GJ has it, I think. But the STANAG ammunition will have to perform identically in ANY rifle designed for STANAG use. Mix a magazine, shoot, no differences.
June 03, 2001, 11:16
No differences other than what can be expected with a magazine full of one country's ammunition.
If you were to pull a dozen rounds of the UK STANAG round, the L2A2, for example from the same lot, I think you'd be surprised at the variations in charge and projectile weight.
June 05, 2001, 17:05
Yeah, but ...
I understand the 4895 example, but it assumes that the 3.44 grain observed variation in powder charges might relate to something like a 300 fps difference in muzzle velocity. This would be reasonable if the ammo was all loaded with the same type powder. But, if I were to load some 7.62x51 with 4895, 4350, and 4320, I could get the same muzzle velocity with widely varying powder charges. While these are not the powders used, the previously mentioned fact that the actual powders are blends (rather than canister powders), makes a comparison based on powder charge alone not completely informative. Comparisons of actual, measured muzzle velocities would be much more useful, and provides a great excuse to drag out the chronometer and do a lot of blasting. :D
June 05, 2001, 18:08
Lot powder is blended as in mixed with powder that's manufactured in a different batch? I always thought that powder was homogeneous in composition. It was my understanding that lot powder is a batch produced to roughly meet the specifications for an order. Then the manufacturer tests it for burn rate and loading for a specific projectile weight, adjusting the charge weight till they get the desired performance. Each batch of lot powder requires a new set of tests. That would go a long way towards explaining differences in charge weight between lots of ammo.
Cannistered powder, as explained to me, is held to much stricter tolerances so as not to invalidate load data derived and published during a previous production run. I have to believe this is true, otherwise anyone who publishes load data would have to conduct tests and re-publish data every time a new batch of powder was produced.
It always scares me when someone has a jug of lot powder pulled from cartridge A. Then they assume that the burn rate is similar to powder B and extropolate a loading for cartridge C. Guessing on this stuff can't be good.
June 07, 2001, 14:23
I agree with what Wadman said. I have a good friend that used to work for the Twin Cities ("TW" headstamp) arsenal, just north of Minneapolis, MN. He said powder would arrive at the plant by the "car load", which I understand to mean a railroad car filled with powder. No mixing of powder was ever done at the arsenal.
Smokeless powder is apparently very difficult to maufacture uniformly, and these bulk shippments each had significantly different durning rates from one another, far greater than is found in commercial "cannister" grade powder. A specific loading charge was developed for each batch of bulk powder that would produce the required velocity within pressure limits for the cartridge being manufactured. Therefore, each lot would have a different charge weight, but each cartridge within the lot would be charged with the same weight (within practical manufacturing limits) powder charge.
Cannister grade powders are held to tighter quality control standards (at least as far as precise burn rate is concerned) which is just one of the reasons for their higher price.
June 07, 2001, 15:57
FWIW, the STANAG required a variation of less than 10% MV, with the American ammunition set as the 'standard' or benchmark.
This means <275 fps from round to round.
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