The only reason I am fooling with this is that I own a half dozen milsurp rifles: a couple FALs, a couple HKs.............. all of which are hard on brass. I thought maybe I could salvage something out of this for shooting out of the autoloaders and not worry about the brass.
At the time I bought this, I was into the local NFA crowd and I went to shoots like Big Sandy and Knob Creek. I figured when I bought it, if it sucked, I would give it to somebody with a belt fed or something. But, obviously that never happened.
Shooting surplus ammunition in a machine gun is false economy, especially if it blows up a $100,000 dollar machine gun. If anyone has not noticed, the supply of machine guns in the hands of civilians was fixed back in the 1980's and the prices of those that are out there have increased several fold.You blow up the registered part of your machine gun, Uncle Sam does not give you a new one. It is all part of the plan, to get these things out of the hands of the public. You can do your thing to advance this plan, shoot old surplus ammunition in your expensive machine gun and blow it sky high.
Surplus ammunition was removed from inventory because the stuff was too dangerous to store and too dangerous to issue. Some Ammunition Technician went through that lot and based on his procedures, determined to remove it from his inventory. American's buy this old crap, thinking it to be "day old bread", and it is not hard to find examples of blown up weapons from old, deteriorated surplus ammunition. It is the gun powder that goes bad, the stuff breaks down, does not burn consistently, and that causes pressures to spike.
Here is some pretty pictures of what happens if that cheap surplus goes kaboom!
A machine gun bud of mine, told me he had blown the top cover twice using 1950's Yugo 8mm Mauser ammunition. He did not know why till I told him of the characteristics of old gunpowder and old ammunition.
I would be very attentive to using any salvaged military surplus gunpowder. I have tossed out about 75% of the surplus powder I bought, because it went bad. It was a total waste of money, but at the time, I did not know about gunpowder lifetime. I am glad the fuming keg of IMR 4895 did not burn my house down. I did not know why it was fuming and I did not know it was dangerous. Old gunpowder, in bulk (like 1lb or kegs) will autocombust and burn the house around you.
The safest course of action is to pour the stuff out, but if you want to balance your safety against the savings of shooting old gunpowder, then shoot it up and shoot it up quickly, and watch for any weird pressure indications. That happened to me with the last lot of surplus powder I had. It was pulled IMR4895, the seller of course claimed it was all new production, or some other lie. I shot the stuff and it shot well, but every so often a fired round would sound different. And I started getting sticky extraction one the occasional case. Then over time, I experienced case neck cracks on fired rounds, and unfired rounds, I experienced 700 cracked case necks on my expensive LC 308 match cases, stuff that had been loaded with the powder for a year. It was in this time frame I met a Naval Insensitive Munitions expert who educated me about the problems of old gunpowder, all of which are bad, bad, bad.