View Full Version : Revisit - Mauser headspace
January 22, 2011, 09:51 PM
So I finally got around to checking out the Mauser again that I wrote about in the thread titled "A Mauser Dilemma". I completely stripped the bolt, including the extractor. With just the bolt body and the No-Go gauge, the bolt closes without any resistance. I tried seeing if a .30-06 case would fit but it would not. I have not taken it to a gunsmith as yet to have a chamber cast done. So, now I'm uncertain again what to do with it. It is in otherwise very nice condition. You can see pictures here:
1916 Danzig Mauser (http://picasaweb.google.com/dhsass/Danzig1916?authkey=Gv1sRgCJiP6eKfkvWyowE&feat=directlink)
January 22, 2011, 10:13 PM
All is not lost just yet.When a chamber is being cut,the gunsmith uses the go/no go to determine if the chamber is initially cut to proper depth.There is another gage,the "field" gage,that determines if the headspace has worn or setback enough to take the rifle out of service.
If you do not have a field gage,and are deciding whether to buy the rifle,well,you know its a little loose.Buying a field gage will work,but maybe for your purposes,see how many thousandths longer a field gage is,then decide how much of that is OK,to you.A shim can be tried between the gage and the bolt.It will give you an idea.
January 22, 2011, 10:53 PM
hmm, you wrote it got "reworked", it looks pretty original to me. Straight bolt handle, long barrel, no 98k cut in the stock for the sling.
Chamber cast is the way to go, but if you know a reloader, have him make you a round with trail boss. Use that, and see if it still looks like a 8x57 after firing.
January 23, 2011, 12:26 AM
I would buy a field gauge and measure again. Field gauges are typically 0.003" longer than factory NoGo gauges.
In manufacturer's lingo, any product outside the factory's possession is "in the field", thus the term "field gauge".
Headspace longer than NoGo, but shorter than Field is acceptable because some lug/shoulder settling is expected to occur during use.
If it swallows the field gauge, I wouldn't shoot it because it can result in case head separation with you getting a face full of hot gas and nasty bits. You could pay a gunsmith to set the barrel back one thread, or take it to the gun show with your NoGo and field gauges in hope of finding a bolt that will headspace properly.
January 23, 2011, 01:53 AM
I already own the rifle. I'm just trying to figure out what to do with it now. My firearms focus has shifted (partly out of necessity) so I don't anticipate buying any more such rifles so acquiring a field gauge at this point just to figure this thing out seems a little overboard. On the other hand, if it turns out to be largely correct rifle for a Gew98 that was reworked prior for WW2 then I'm going to have to think more seriously about keeping it. The bolt is correct, although not matching numbered. It does have Imperial inspection marks under the bolt handle root thereby making it a little more than just a correct straight handled bolt. The stock gives me pause though. Shouldn't the butt of the stock have a bolt take-down washer to be correct? I know K98s relatively well but I don't know these Gew98s that were reworked for the war. Maybe I'll ask around and see if I can't find somebody locally who might have a field gauge.
I suppose, if I could find a tire, I could try the tie-the-gun-to-a-tire-and-fire-it-with-a-string trick and see what happens.
January 23, 2011, 10:59 AM
Cut a round piece of standard masking tape and stick it to the (case head) end of the No-Go gauge then check your headspace again using that striped bolt.
Any resistance when closing? If so, measure the thickness of a new piece of tape and let us know what you find.
January 23, 2011, 01:35 PM
This from a longer note I wrote on headspace:
". Two gauges (or gages) are used at the factory and by gunsmiths to ensure that the chamber and bolt are within specifications for the cartridge. These are called the "GO" and "NO-GO" gauges. Their use must be understood in terms of the tolerances of the cartridges that the rifle will use.
The GO gauge ensures that the rifle will close and operate with the longest cartridge that is within tolerances for the ammunition. The NO-GO gauge ensures that the shortest cartridge that is within tolerances will not be allowed to stretch far enough to exceed the elastic limits of the case material.
But we mentioned that normal use of the rifle will cause changes in the dimensions of the locking system and the locking seat(s) in the receiver. That fact led to the development of a simple "one gauge" test to ensure that the rifle has not become dangerous. This test is by use of a FIELD gauge. A rifle that accepts a FIELD gauge may be nearing, at, or past the danger point; the only way to know which is by knowledge of that rifle, or by the "feel" of the gauge. At best, failure of the FIELD gauge test delivers a warning, like the wear ridges on tires. At worst, it signals certain danger. Even a rifle that fails the FIELD gauge test may function normally with cartridges at the long end of the cartridge tolerance, yet be dangerous with cartridges at the short end."
January 23, 2011, 09:40 PM
Mr. Keenan is right. To top it off the chamber specs in a Mauser and the ammo specs designed for that Mauser are not the same as U.S. specs. This was gone over before and anyone that tells you different is wrong. Even U.S. Military and commercial specs are different. I don't think I ever had a Mauser pass a no-go gauge made to SAMMI specs. Go into the Brownells catalog, buy some Cerro-Safe and make a casting. This stuff is really easy to use.
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