Thursday, August 23, 2012

Looking at case stretch in an elderly 8mm Mauser...

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Recently I decapped and polished 110 cases for my 8x57mm Turkish Mauser. This is one of the rifles I shoot in the high power match, and these are my match cases for it.

This is not virgin brass..... far from it.

It's so far from virgin that I'd have to wash my mouth with soap just describing their level of 'experience'. They are headstamped MM 7.92 42, and that makes them of Canadian manufacture from 1942. Yes...
I said 1942.

I shoot 70 year old cases in my 60 year old match rifle. Get over it. I'm cheap.

The thing is... on examining the cases as they came from the polisher, one had a blemish going around the circumference of the case. That is one possible sign of an incipient case head rupture, and has to be taken very seriously.

I sacrificed one of the cases to the diamond saw, and sectioned it for examination of the case walls. I was shocked to find the brass shows absolutely no sign of stretching at all. This after being fired from the original military loading and another six or seven of my match loads which involved a case overstuffed with IMR 4350.

I attribute this to neck sizing almost every time, with one full length thrown in at the start. A bout of annealing didn't hurt either.

On another note, for polisher media I tried something new. Solid plastic pellets made for rock tumbling and polishing. Maybe a sixteenth of an inch around, with a seam that's slightly rough. I gave them a spritz of Ballistol before the polish session, and the cases were mirror clean in an hour or so.

What makes the plastic pellets so special as a media..... when it gets dirty I'll be able to rinse them in hot soapy water, dry them in the sun, and keep right on using them with no end in sight. That makes them cheap....

Remember.... Carteach is cheap. (g)



4 comments:

Old NFO said...

Nothing wrong with cheap as long as it's safe!

drjim said...

Thanks for the interesting case autopsy.
As a rank beginner in reloading, yours is one of the sites I come to for knowledge and guidance.

James said...

I enjoy your blog very much,and look forward to your posts.

Have you ever heard the "tale" of the Canadian 8mm? According who you listen to it was made for a foreign power I've heard a couple of different states named. At any rate the contract fell through and the CIA stepped up inn the early 50's and bought it up. They had more made, but had the 1942 headstamp kept on the new run. It was packed in plain brown boxes and issued to anti communist forces in south and central America along with captured german arms from WW2.When the Bay of pigs fell apart and Castro figured out that the mystery ammo came from the CIA the cover was blown and the ammo was dumped on the surplus market (via Israel in one version) Bottom line, a great story and I bought 2 boxes!

GreyLocke said...

What is the plastic pellets name? Might be interested in them.