I bought a Yugo 8MM Mauser 48A that looks pristine other than the stock have some usual dings. All parts match-bolt, barrel, and trigger group. All look like new and the barrel has excellent rifling. After firing about 12 rounds at the range I noticed the cases would not fit back into the plastic holder provided by the manufacturer. When I got home I took the calipers to find out what I thought had happened. Sure enough the necks were expanded .008 thousands of an inch. The gun functioned fine and no excess pressure was indicated with primers, case buldging, firing pin cratering, etc. just the expansion of the necks. I'm using Remington 8MM Mauser 180 grain bullets. Do I have an over sized chamber at the neck or am I not using the right bullet? And is this a problem/safety concern? I really don't think it would be a reloading problem as the rest of the case miked out OK. Thanks, Mike
Posts: 919 | Location: USA | Registered: 22 May 2002
Bad luck I suppose - most of them have great chambers. I suppose you could just neck size your cases.
FWIW, all M48's have the .323 (JS) bore size. The only rifle I'm aware of with the J bore (.318) was the 1888 Commission rifle and the first few years of the M98 (until 1905).
Posts: 498 | Location: Georgia | Registered: 13 January 2002
Buzz, you're right about military weapons. But, for some unfathomable reason, the German gunsmiths created a bunch of J-bore sporting rifle barrels long after the S bore became the standard military bore. So there are a lot of custom, commercial, or "gunsmith-made" "8mm" rifles (not just 8X57's, by the way!!), that have .318" bores. Whenever one encounters a non-military "8mm", it is a good idea to slug the bore. (Something a lot of people don't often know is that in Europe, a lot of early smokeless powder rifles used undersized BULLETS. For example, although the "J" bore 8mm 1888's used .318" diameter bullets, the RIFLES generally had a GROOVE DIAMETER of .321" to .322". Such rifles, if they have a generous enough throat diameter that, when fired, fully release the bullet, can safely use .323" bullets with loads using slower powders such as 4350!!)
Here again, and after miking the cases have found out the necks are .010 larger than new ones. Fired case necks are .357 versus unfired Remington at .347. Bullets mike out at .322 on both foreign and US manufactured ammo. Thus, I'm guesssing the bore is .323. Is the .010 expansion on the neck of the ammo a dangerous situation? I know .010 expansion or stretch lengthwise shows excessive headspace which is supposed to be a big "NO NO". Thanks for the help. Mike
Posts: 919 | Location: USA | Registered: 22 May 2002
No, no! Overexpansion of a neck won't hurt anything, except perhaps accuracy!! It's when the case mouth doesn't expand enough to freely release the bullet that interesting things start to happen!!
Eldeguello is right. The only real function of the neck is to hold the bullet into place until its fired, headspacing is only effected by the shoulder. Chances are what youve got is some thin brass at the neck. I have some Equatorian 8X57 millsurp ammo that measures .351 at the neck before being fired and .358 after, where the shoulder meets the outer case they are only .420 before firing but .431 (exactly what its supposed to be) after firing.
As long as the headspace is OK then this is no different than fireforming an AI case and is perfectly safe. If you have any further doubts then have the headspace checked by a gunsmith, otherwise enjoy your Mauser.
Thanks for the information. If it has "pie plate" accuracy at 100 yards with the open sights, good enough. And anything better than that will be frosting on the cake.
Posts: 919 | Location: USA | Registered: 22 May 2002