Walkalong
bigedp51's nice pic of a setup to measure the rut.
Walkalong
Not only do I take fantastic photos, I'm very good looking, exceedingly brilliant, and also very modest.
(and I also have brown eyes)
Michael R.
Below are .303 British cartridge cases, from left to right, A brand new unfired case, fired once and fired three times.
On the third firing the case head above did not separate but look like the stretch marks your wife gets before the baby comes.
Below is "half" of a case head separation, on the back side you can't see its not cracked all the way and is only stretched.
This is what a factory loaded Winchester case looked like on the first firing, this case stretched .009.
Case head separations happen all the time and there is a "BIG" difference between this and a catastrophic case failure that dumps 50,000 cup back at your face. Below is a stuck case remover for .303 British cases that have had a case head separation.
Below is a Enfield rifle with a reloaded case that is about to separate (see my case that was reloaded three times above) The Enfield rifle had a piece of tablet paper wrapped around the receiver to show how the gas venting system works on the Enfield rifle.
Below the exposed paper showing scorch marks and the case head separation.
As you can see the paper was not blown to smithereens, the shooter was not injured in any way and the only damage might be brown stains in your underwear the first time it happens.
The trick to reloading is experience and having the tools you need to "read" your cases before and after firing. The Enfield rifle is a extreme example and the Enfield chamber was enlarged during WWI to make room for the mud of Flanders. Or chambering a cartridge is like parking a Volkswagen beetle in a blimp hangar.
When reloading and full length resizing you only need to push the shoulder back .001 to .002. If you push the shoulder back more than this the case will stretch in the base web area and this will lead to case head separations. This means you do not set the die up to contact the shell holder as the instructions state. The resizing die is made to push the shoulder back .002 below minimum headspace so all resized cases will fit in the chamber. If your rifles headspace is .003 over minimum you will be pushing the shoulder back .005 every time and the case will stretch and separate much sooner.
Nothing is written is stone, case head separations are governed by headspace, the size of the resizing die, how the case is constructed, meaning the diameter of the case and the case wall thickness.
Below is from Reloader Magazine
Please notice NO ONE died while testing these cases.
BUT safety glasses are a must for safe shooting of reloads. And new cases should be used when hunting for 100% reliability. All it takes is one defective case to screw up your hunting and you don't get a second shot if you have a case head separation when hunting large bears.
P.S. Don't even think about using old reloads and carrying pepper spray as backup for a ruptured case in bear country.