Mil-surp 7.62 brass way out of spec

[NCHillbilly]

Has anyone else out there been using recent issue military pull down 7.62 brass? I bought about 400 cases,mostly LC 13, and about 20 percent of the cases won't come anywhere near fitting my chamber gauge. I can remove my decapping pin and resize them(with primers intact), but I haven't shot any yet. I don't know whether to expect any issues. These things were really not close to being correct. They've never been fired, so I'm curious as to how they became so oversized.

 

[dauntedfuture]

MIL brass has thick necks, bullet sealant, a crimp and high neck tension. When the bullet is pulled out it stretches the neck out. You can do the same thing if you don't lube the inside of your case necks, your expander ball can bull the shoulder forward, especially on LC brass. You should FL size all new brass, and based on what you are saying this brass too. A shoulder bump die will work too. I suspect that other than the shoulder moved forward the brass is on the slim side and you will not feel much resistance on the brass when you size it until you hit the shoulder.

 

[NCHillbilly]

MIL brass has thick necks, bullet sealant, a crimp and high neck tension. When the bullet is pulled out it stretches the neck out. You can do the same thing if you don't lube the inside of your case necks, your expander ball can bull the shoulder forward, especially on LC brass. You should FL size all new brass, and based on what you are saying this brass too. A shoulder bump die will work too. I suspect that other than the shoulder moved forward the brass is on the slim side and you will not feel much resistance on the brass when you size it until you hit the shoulder.

I considered a lot of the reasons you gave for this condition, what confused me was I was only seeing this problem with about 20% of the cases. I do make a point to check all pull down brass with a Wilson chamber gauge to be sure.

 

[pawprint2]

some of the machines used for pull down, actually push down on the bullet prior to the up stroke, these are big presses running more than one line on a given stroke. The bullet sealant, on mil ammo can be a pain in the ass on tear down. When looking at the old 50 bmg- you could scrape out a fair amount of tar from the necks. Dauntedfuture, is right on with his advice, size all your pull down brass with same die in one operation from the start. Good idea to prep all your 400 pieces from the start, primer crimp, neck trim, and check flash-holes for burrs. Now you have a zero starting point, good luck!