View Full Version : Mauser 98 Headspace?

December 9, 2005, 03:01 PM

I have a problem with a nice KAR 98 Mauser that I need some expert advice on. I traded for this gun and got into it for very little and it looks very nice. It has been sporterized and has a nice walnut stock. Very professional job. I sold it to a friend of mine for his son to shoot and was on a deer hunt when we were target practicing with it an it would not hold a 6" group at 50 yards. The scope was ok and the bore looks very good. I got the rifle back and gave him his money back and sectioned some of the empty brass when we got back. The primers (factory loads - very mild) had backed out quite a bit. Also, there was a very noticable buldge on one side of the case and it appeared to me (in the section) a thinning of the brass in this area.

The primer protrusion could be from underepowered ammo, though I doubt it with factory ammo. It probably has a headspace problem and/or a buldged chamber. I guess all of this could be caused by bad headspace.

Anyone care to redender an opinion or a guess? It is a nice rifle. Need to get it fixed and/or rechambered and shoot it. Thinking about an 8MM-06. I didn't want to sell it anyway!


December 9, 2005, 06:20 PM
There may be a smith close by that has a set of guages, but these days that is unlikely. You can purchase a set from MidwayUSA, Brownells, and many different other places. It does sound like you have headspace, but I have yet seen headspace cause that kind of accuracy problems. I would check it out further before deciding that was the only problem. You could have a bad crown on it or have a serious bedding problem or a bolt that is touching somewhere it shouldn't be or some other malady that is causing the bad accuracy from something as simple as a badly fouled bore.

Most of theK98's from later years of the war weren't built to the same specs as the earlier ones were. By that I mean the quality of the craftsmanship wasn't the same nor was the quality of the materials being used. A lot of them have had diferent bolts swapped into them or replaced just the same when a bolt was lost or had a problem. This usually wasn't a problem on a miitary rifle which didn't need to reload a piece of brass so it isn't unusual to find one that has a problem with headspace being excessive to the point the primers will back out. I would seriously have a look further into the rifle to figure out what is wrong.

The 8mm'06 is a fine round and you should be happy with it if that is what you are after, but you should at least have the rifle checked out for other problems and not just the headpsace. On average with open sights, mine have usually shot at 100 yds into a group of close to 3" which isn't a bad military rifle group, some do better, but that is an average group. Don't hold high aspirations for the rifle to shoot minute of angle groups, it may not ever shoot that good, but a decent group like mine is the norm.

I did do a .308 for my son last year that shoots 3/4" groups at 100 yds with a scope so the receiver is capable of better groups, just the barrel may not be. Good luck with it.

James K
December 9, 2005, 06:31 PM
I think you have a headspace problem, but I doubt it is causing the inaccuracy you mention. The primer backing out is caused by the headspace problem in combination with the mild load of American factory ammo. When the gun is fired, the firing pin drives the case into the chamber. The primer then ignites, and its pressure forces it to back out. Then the pressure in the case forces the thin sides of the case against the chamber walls, while pushing the base of the case back. That forces the case back over the primer, and the pressure can tear the head off the case if the headspace is excessive enough.

In your case, because of the mild load, there is not enough pressure to force the head back and stretch the case and also not enough pressure to force the case back over the primer, so the primer is protruding.

But you definitely have excess headspace. A heavier load could have caused a real problem.


Harry Bonar
December 9, 2005, 07:53 PM
Dear Shooter:
Jim Keenan has it.
The Germans didn't care too much about real tight headspace. But, your innacuracy problem isn't caused by this.
Four variations of the 7.9 (or 8mm) Mauser round.
8X57J - .318 groove.
8X57JS - 324 groove.
And a rimmed version of each.
I'm more concerned about the "bulge" in the case - this rifle may have been re-chambered for some variation (possibly 8MM-06) and the extractor is just holding the case back to fire! This needs a cerosafe cast made of the chamber before you fire it again to really find out WHAT this Mauser is chambered for.
I've never in 50 years seen a Mauser out like this in headspace! I "think" you've possibly got a re-chambered rifle.
Harry B.

December 12, 2005, 04:48 PM
Thanks Guys,

I was thinking of doing a chamber cast first. It never occured to me that it could have been rechambered but that certainly is possible. I'd rather not blow myself up!