Oversize chamber/bulged case - worry?


May 30, 2003, 01:05 PM
Last week my brother and I took a war-trophy Arisaka Type 38 Carbine to the range to shoot. The gun came back from the Pacific w/my grandfather, and my dad says that a number of my grandfather's buddies used it in deer camp for a # of years. I detail stripped and cleaned 40 yrs of grime off it some time back, and everything appears fine. W/the bolt removed, hand chambered rounds fit flush w/the chamber, tho there is a little side-to-side play. We loaded it w/new Norma 139 gr ammo at the range, and I let my brother have the first shot. When we checked out the ejected case, the case wall had bulged near the base, abt 3/16 up from the groove. I measured it at 0.455", which is listed as the mil spec case's base diameter in one of my books. Unfired brass at the same point measured 0.444", so there was abt 0.011" expansion. Is this enough to worry about?

I've read a few similar accounts on various boards abt folks with oversize (not reamed) chambers in Arisakas, and that Norma brass may be a bit small. I thought perhaps it had been rechambered to the 6.5-.257 Roberts wildcat, which was apparently pretty common for Arisakas back then, but the a) chamber dimensions don't match (i.e. dia too small), b) my dad said my grandfather never reloaded and c) he'd never seen any of that ammo around the house growing up. There was no evidence of excessive pressure that I could see, and no other case deformation (length, neck dia and shoulder all as unfired).

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May 30, 2003, 01:57 PM
it's an Ishapore .308. The loose chamber is designed to help it feed dirty ammo in wartime(or so they say). And My cases come out a little flexed but I still use the gun. Makes me a little nervous.

All I can say is I would take some of the bulged cases and the rifle to a competent gunsmith and get advise. I should do the same just to sleep better at night.

As I understand Wartime Arisakas, they were poorly Quality controled and the Japanese soldiers often had to sit with a pile of poorly sized ammo and match good fitting ammo to the gun by hand. YIKES! Or that was what I saw on the history channel anyways.

Good Luck!

Jim Watson
May 30, 2003, 02:04 PM
Are you going to reload for it or just fire a few factory loads on "ceremonial occasions?"

If the former, send some fired cases to a die company like RCBS and get a set with a sizing die no smaller than necessary to get them back in the chamber.

If the latter, I doubt there is much risk of casehead separation on the first firing of a factory load.

May 30, 2003, 03:43 PM
I have the same issue with a Mosin Nagant M38, although the bulging only seems to be around 0.005". The rifle passes a poor man's headspace check (two pieces of masking tape on the back of a cartridge, bolt doesn't close).

BTW, the ammo I was using was S&B, 180 gr. softpoint. Bulge is enough to make extraction a little difficult.

However, extraction was not as bad as what I have experienced with Czech silvertips and one of my 91/30 MNs. The first round was OK, the second sticky, and by the third I had to smack the bolt handle with my fist to get it open. Clean the chamber, and repeat the process over again.:cuss:

May 30, 2003, 07:24 PM
Thanks for the replies. It'll be for "ceremonial" shooting only, so I probably won't sweat it. Extraction was easy, according to my brother. I let him shoot it first as kind of an honor, since it was last used by our long-dead grandfather, and after seeing the bulge he was instead convinced that I did it in case the rifle blew up. He has such a persecution complex. Must be a little brother thing ...

The Type 38 Carbines date from the early teens thru late 30's, and are of better quality than the mid-late wartime rifles. It's actually a pretty solid looking gun - well fitted parts, etc.

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