Macd wrote:...........
3. Stress Cracking or Seasoning
This is a combination of the residual stresses left in the brass from manufacture and loading combined with chemical attack by ammonia. Ammonia may be present in man made materials particularly some cleaning products, in the soil or anywhere animal urine decomposes releasing ammonia into the surrounding air. Humid conditions accelerate this process. As brass hardens its elasticity decreases and neck tensions increase adding more stress to the case..........
............annealed by induction rather than flame..............
.........
Brasso has ammonia in it - or at least it used to. I caught a guy using it in his tumbler and he liked it so much he tumbled thousands of rounds of brass to clean it all up and make it pretty. A couple years later he started finding split necks on loaded ammo - lots of loaded ammo. I attribute some of the splitting of some of the very old brass I had to that because he and I swapped components and casting/handloading tools for years. I finally got all the old brass segregated and recycled after a few years. We were both working on 257 Roberts rifles at the time, so my exposure was limited, although interesting.
Sometimes, the brass looked fine, but when fired, I would get three-inch groups at a hundred yards with a rifle/load which usually produced sub-half-inch groups. Other times, I'd pull a cartridge out of the cardboard box and the neck would be split all the way to the shoulder and the bullet welded to the inside of the case neck with verdigris.
I've left very old brass loaded for decades, especially in the 257, without necks splitting and the neck area in my chamber is wide. The throat is long too, so when I neck-size, I only do about two thirds of the neck for 75 grain HPs and it looks like I'm loading to fire-form brass for a wildcat - there's an extra "shoulder." OK, that's an exaggeration, but it's very visible. So, I had been really working my brass over. The 257 isn't
too hard on brass to begin with (low pressures), the old brass was probably high quality, but the addition of the ammonia on some of it just wasn't helping things at all.
I'm no chemist nor a metallurgist, but both a chemist and metallurgist have told me that ammonia is very hard on brass, so I knew better. Felt bad for the guy who ruined almost every piece of bottle-necked brass he had, to include a very large lot of good ol' National Match '06.
Dang! Induction-annealing! I never thought of that. I know wheel spindles (and other automotive parts) have been induction-
hardened through industry my exposure, but never thought of doing brass that way. I used to know the basics of the process for wheel spindles, but forgot. I do remember that a spindle can be turned cherry-red in part of a second. Hmmmm, how to do this without electrocuting myself..... And I just promised an old Lincoln Buzz-Box to my brother. Bet that has some componentry that would be helpful....
No,.... That's too much like work to figure it out and I'd end up with big a collection of brass puddles before I ran out of cases trying to get it right.