kaboom

[Ned christiansen]

I have a couple random, unqualified thoughts here.

LouBoyd, just to put your 70,000 PSI figure in context, a friend of mine did some pressure testing to quantify the effects of shooting 5.56 NATO ammo in a .223 SAAMI chamber, and he regularly got 72K and even got above 76K! This happens thousands of times a day all across the country.... which is not to say that the occasional "unexplained" KaBoom doesn't take place because of it.

I know this thread is not about .223 but I thought this might build some context around your numbers.

But check this out: me, shooting 240 SMK handloads. I recover one from gel and observe an odd "waist band" on it. I look and think, think and look, and measure it. The bullet diameter is reduced to .299 in this area, and this area occurs just below where the neck of the case would be holding the bullet.

When loading this batch, I had decided, no more 240 SMK's, they are just too dang long. It was too much finessing to get the bullets seated deep enough-- what with powder being in the way (I considered for a moment, what if I just started them all, then turned the press upside down, so the powder would not be blocking the seating of the bullet?).

So there I am with some 240 SMK loads, the base of the bullet practically capping off the flash hole. There is little to no powder under it, it's all to the side.

My Bubba-tastic conclusion here: As pressure built in the case, there was plenty of bullet shank for it to act upon, and very little base. Before bullet movement started, giving the pressure an avenue of relief, the pressure actually pressed on the bullet shank, collapsing it. This (to me) explains why this only happened from the bottom of the case neck down.

Now-- if this could happen this much, could it not happen some more? An event whose timing is just a little different, say the bullet delays even more in getting moving, the waist of the bullet caves more, and the displaced metal moved down, increasing bullet diameter, adding to the problem?

I'll find the pics of this bullet and get 'em up.