Sunday, October 5, 2008

8x57mm case stretch... amazing



Today I decapped and polished 110 cases for my 8x57mm Turkish Mauser. This is the rifle I shoot in the high power match, and these are my match cases.

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 66 year old cases in my 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.

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.... carteach0 is cheap. (g)

8 comments:

Old NFO said...

Interesting... I'd hate to try that with the cases being made today. Sigh... I REALLY wish I could reload, but that isn't going to happen until I move.

Somerled said...

I'll have to try those plastic pellets. Mice have gotten into the walnut hull media when I buy a large batch and can't get it all into airtights. The wash-n-dry plastic wouldn't take up as much storage space because I wouldn't have to stockpile replacement media.

What sort of neck sizing die are you using, carteach? I've been using the Redding deluxe sets with both the FL and neck sizers. I've never used the collet neck sizing dies.

Carteach0 said...

Somerled,

I've been using the Lee collet type neck dies. I like the idea of squeezing to a mandrel rather than squeezing into a die hole. and pushing back out to size. Less brass push, less wear.

They seem to work well, but I have never checked for concentricity. Have to build a DI gauge for that one of these days.

I post updates on the whole plastic bead thing, with a source if I can.

The Hermit said...

I always full length size my brass because I have a number of Mausers. I have heard that neck sizing only works well if you shoot the same round out of the same rifle every time.

Carteach0 said...

Hermit,

You heard right, but often we get lucky. Two out of Three of my 8x57mm Mausers will shoot the same neck sized cases.

I full length size for my semi auto AR180b as their chambers are tight and they need min-spec ammo to chamber reliably.

If you get good case life with full length sizing, then no problem and life is good. For me, I get better life and accuracy wit neck sizing where I can.

JAFO said...

I'm a new reloader as well. Can you post any pics of the "blemished" cases? I am not sure what to look for externally to warn of oncoming failure.

Carteach0 said...

Jafo..... you have revealed me in a moment of stupidity. I didn't photograph the blemish that caused my concern.

The next time I see one, I will. I should probably make a collection of case failure photos and then write a post about them, rather than just chucking them in the scrap brass can.

JAFO said...

I'd love to see such a post.

Isn't it possible to check for case stretch by using a caliper as well?

If the case wasn't failing, what caused the blemish?

Thanks for any info you can provide. As I said, I'm a new reloader and would sure like to avoid catastrophic case failure when my eyes are in proximity!!