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Brass Expansion Question - Cartridge Web

Posted: Mon Nov 04, 2013 1:30 pm
by Obsessive
Hello, all - I finally got a chance to take my new (to me) Mauser to the range today for a function check.

I was shooting Yugo 53' vintage surplus that I was given (40 rounds) after the purchase. FYI, I properly checked the headspace before firing the weapon (I purchased a Field Gauge).

I'm seeing a small amount of expansion of the brass near the base of the cartridge. I'm assuming the limited amount of expansion I'm seeing is normal and may be due to the surplus ammo. I have a Mosin that exhibits the same thing with surplus ammunition. I have checked the interior of the cases, both by visual inspection (interior) and by the 'paper clip' method, checking for any grooves, cracks, etc. on the interior of the case - I found no issues with any of the 40 rounds I fired. I the primers do not protrude beyond the cartridge face but a few look slightly flattened. No cratering.

I am seeing around .004" of growth of the cartridge at the base. Is this normal? The growth is the same no matter where the measurement is taken. Again - there are no signs of tearing/cracking/etc.

The rifle shot like a dream - nice groups @50 yards for surplus 53' ammo. Time to get some decent stuff... Also, the recoil was just fine. I find it more comfortable to shoot than my Mosin by far.

See pictures below and let me know what you think (Obsessive, maybe??? :D )

Unfired (empty but primered) brass on bottom.
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Unfired brass on right.
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Unfired brass.
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Fired brass.
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Cut. Note that there is some chamfering on the outside in a few spots (evident at left bottom side of the bottom cartridge) because my dremel wheel slipped. It is not thinner in this area.
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Re: Brass Expansion Question - Cartridge Web

Posted: Mon Nov 04, 2013 2:55 pm
by Obsessive
Broken link above (won't let me edit for some reason)...

I also decided to look up the SAAMI specifications on the 8MM Mauser cartridge. It states that the web area of the cartridge should be .4698" and the chamber should be .4710" - I'm assuming the expansion I saw is simply the cartridge filling out the chamber to it's spec since the ammo appears slightly undersized compared to SAMMI specs (.467" on the Yugo vs. SAAMI .469")

For craps and giggles, I cut two of the cases open that were .471" to look inside. No signs of overpressure or separation from what I can tell.

Cut. Note that there is some chamfering on the outside of the cut in a few spots (evident at left bottom side of the bottom cartridge) because my dremel wheel slipped. It is not thinner in this area.

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Re: Brass Expansion Question - Cartridge Web

Posted: Mon Nov 04, 2013 3:17 pm
by boltaction
Hello, If I am not mistaken, that is normal. If you reload the FL die takes care of this. You are right about paperclip trick to check for signs of head separation when reloading,,, thinning of wall ahead of the webb. A problem seen with belted mag. ammo. 300 win mag 7MM ..

Re: Brass Expansion Question - Cartridge Web

Posted: Fri Nov 08, 2013 12:50 am
by Ironnewt
You did a nice job showing what a Berdan primed case looks like.