Ka-Booms

Sunday was range day and I had eight men out shooting clays and cardboard.  Generally these shooting affairs are droll and boring.  We shoot some cardboard and clays and then go back into the "Pistol House" gather around the stove and shoot the breeze until we can feel our fingers again and then repeat.

This weekend we had some excitement.  We had three Ka-booms.  For those not in the know this is when there is a catastrophic failure of the cartridge which may or may not damage the pistol and/or the pistol holder.  All three instances involved separation of the cartridge head from the case.  In the first two instances the Ka-booms happened in a Springfield XDM.  The first Kaboom obviously didn't damage the gun and the second blew a roughly triangular piece out of the grip about an inch across and three quaters of and inch high out of the top of the grip.  Other than some powder burns and some numbness in his hand the shooter was uninjured although he now has a seven hundred and fifty dollar paperweight.  Thank God he was uninjured!

The third Kaboom happened in a Glock 23.  In this instance the case separated and blew out the magazine.  the mag release, and the mag release spring.  Again, thank God the shooter was uninjured.

In all three Ka-booms the we managed to find the head and examine it.  In each we lined up the marks from the extractor with the orientation of the extractor in the firearm and it was obvious from the powder residue marking the head that the failure occurred on the ramped portion of the barrel.  That is holding the firearm in it's normal orientation (not gangsta style) that the case ruptured at six o'clock.

I've read that .40 S&W is prone to failure in early Glocks due to the cartridge being unsupported at the ramp but the newer Glock's and XDM are both supposed to have well supported case heads. Apparently some cartridge manufacturers have beefed up the case walls in the area immediately forward of the head.  I've also read that .40S&W can double the pressures if the bullet gets pushed back into the cartridge (this can happen with any cartridge of course).

Cartridge	Max Pressure (psi)
9mm +P	35000
.40S&W	35000
.45ACP	21000
.454 Cassull	65000

Looking at the SAAMI pressures for various handgun rounds you'll see that a fully supported revolver cartridge can have much higher pressures than a similar auto cartridge.  I think all things considered maybe the proponents of .45ACP are onto something.  Not necessarily for the reasons they assert.  My next pistol is going to be a revolver though.