Headspacing 1950s Mauser Action?

J

jmstr

New member
Hello All,

Just got my Clymer Field gauge [.308] to do some headspace checking on a couple of rifles.

The first one I want to check is a Mauser 98 action, chambered in 7.62x51.

I realize that the numbers indicate a .308 FIELD gauge is actually about the same as a 7.62x51 NoGo gauge. However, I have a few .308 lever/semi's to check later- so wanted one tool for all. The others are Garand [yes, in 7.62x51], Saiga 7.62x51 and Savage 99F in .308.


Two questions.

Does the Mauser extractor HAVE to be removed to use the Clymer Headspace gauge?

I notice the Clymer HS Gauge has a rim cut in it for the extractor, and was able to slide the gauge up under the extractor rim.

I was able to use it, UNDER the extractor claw [i.o.w., with extractor holding it to the face of bolt], and the straight bolt went in and pivoted from 12 oclock [up] to between 1 and 2 oclock [or 45 degrees down], before it stopped. I didn't FORCE it, but brought it to where moderate resistance was felt.


The second question is about how many degrees of an arc does the bolt handle make between a NoGo and a Field Gauge [between about 1.635 and 1.638"]?

Would the amount of rotation in the 'lock up', indicate that the NoGo would go into chamber, but the lugs would not begin to engage [45 degrees of rotation difference between them], or is the difference between a NoGo and Field more likely to get the straight bolt handle to point from 12 to 1 oclock [about 15 degrees difference between gauges].


I am hoping I don't need to remove the extractor, but will do so IF I HAVE TO.

Any tips on what to expect?

Again, this is a Spanish FR8, which is a 1943 Spanish Mauser, that is basically a K98, which was rebarreled [with a Cetme front sight post/bayonet lug/flash hider] into 7.62x51 around 1955. Functionally, it is a Mauser, even if it technically isn't.

thanks in advance!
 
No, you do not have to remove the extractor to check headspace. Typically, when checking headspace on rifles with plunger style ejectors, you remove the ejector (not the extractor), but Mausers do not have plunger ejectors.

You are correct, do not force the bolt down on a no-go or field gauge. The rest of your question does not make sense. Once the bolt gets past the camming surfaces, the bolt lugs and lug recesses in the action are perpendicular to the bore, so if the bolt closes, it closes. It does not get tighter as it closes.

And the FR8 really is a Mauser, it's just dressed in drag.
 
Sometimes..if something only needs to be done once,right,its best to let someone who knows what they are doing handle it.
Yes,you strip the bolt.You take the cocking piece and firing pin out.And its really not difficult to R+R the extractor.Its unacceptable for the extractor to crowd the gage off center.If there is clearance ,gage to extractor,OK.
You want all surfaces involved clean.It does not help to measure over dirt.A light oiling,light oil,is good inside the chamber,etc.

Yes,there IS camming ation as you initially engage the locking lugs.
And yes,you might be able to do a certain amount of crushing in:eek:,but that is not the way to use a gage.The bolt should close freely on the go.
With a light touch,if you feel any resistance,you are on the gage.Gentle,fingertip pressure,almost gravity.
"GO" the chamber must freely accept the gage."NoGo is the high limit of production tolerance....when you build the gun.The nogo is for the gunsmith to checkhis work.The "field"is what you use(theoretically) to take the gun out of service
 
Thanks all,

The chamber and bolt were clean, and I 'centered' the gauge as it was going in.

I moved it slowly into the chamber and slowly began to move the bolt lever down/to the right, where it moved smoothly to the 45 degree angle I described. I did not use 'light and delicate' pressure, but it was still what I would think most people would call 'light'.

After a lot of diverse projects, such as setting manually adjusted valves, I know that it is hard to do delicate and strong. And I also have a feeling for very light.

I DID use the term 'moderate resistance was felt', but I really meant, in retrospect, the first point I felt resistance more than I would feel with an empty chamber. Even with no gauge/snapcap/live round, I feel some resistance, as the lugs engage. This was a bit more resistance than closing a bolt on air, and that is what I called 'moderate'.

In my mind, I believe I followed HiBC's comments about this.


And thanks. From my previous experience with my Chilean '95 [in 7x57, as designed], I was pretty confident that there was a slight 'camming' action in the design, as the bolt is rotated, to generate a tighter bolt/chamber fit.

The idea that the bolt handle should just 'drop down' all the way made me think the gauge would be too short or that the bolt lugs had setback.

Thanks all for your rapid responses!
 
Sometimes..if something only needs to be done once,right,its best to let someone who knows what they are doing handle it.
Yes,you strip the bolt.You take the cocking piece and firing pin out.And its really not difficult to R+R the extractor.Its unacceptable for the extractor to crowd the gage off center.If there is clearance ,gage to extractor,OK.
You want all surfaces involved clean.It does not help to measure over dirt.A light oiling,light oil,is good inside the chamber,etc.

Yes,there IS camming ation as you initially engage the locking lugs.
And yes,you might be able to do a certain amount of crushing in,but that is not the way to use a gage.The bolt should close freely on the go.
With a light touch,if you feel any resistance,you are on the gage.Gentle,fingertip pressure,almost gravity.
"GO" the chamber must freely accept the gage."NoGo is the high limit of production tolerance....when you build the gun.The nogo is for the gunsmith to checkhis work.The "field"is what you use(theoretically) to take the gun out of service
Click to expand...

^^:)

Anything that causes resistance to the "feel" of the lugs engaging, or the boltface contacting the gauge needs to be removed. And as he says- esp on an old rifle, clean is critical. A shotgun chamber brush followed by a mop is great for this on an old milsurp.
 
Clean and also a completely naked bolt - get all the bs off it. That way gravity will let it close with a nice solid clank. Any mushiness and you know the gage has filled up the space.
 
We were taught to strip out bolts when we checked for headspace. It should not close on the field gauge. If it does, then the barrel should be set back and rechambered.
 
Even closing on a Field gauge is not a cause for panic; it is like testing a tire with a tread gauge. A failure means you start to look around for a tire sale, not that you abandon the car then and there.

The trouble is that if the rifle fails a Field gauge test, it is sometimes hard to tell by how much. Just closing will be OK; closing with a lot of space is another story. Examining the fired cases will give a better indication of how serious the problem is. FWIW, headspace problems on civilian rifles are about non-existent; they just don't get fired that much. Even the military's main headspace concern was with machine guns, not rifles.

As to removing the extractor, that is not really necessary, IMHO. (Removing the firing pin and spring is a MUST, though.) The slight amount of side pressure does not affect the results, and in many cases, removing the extractor can cause other problems. I once saw a gunsmith remove the extractor on an M1903 to check headspace, then beat up the collar by ramming it repeatedly into the receiver. He would have better left the extractor on.

Jim
 
The trouble is that if the rifle fails a Field gauge test, it is sometimes hard to tell by how much. Just closing will be OK; closing with a lot of space is another story. Examining the fired cases will give a better indication of how serious the problem is. FWIW, headspace problems on civilian rifles are about non-existent; they just don't get fired that much.
Click to expand...

True that.
One could add layers of tape to the casehead to determine how far...
I've installed McGowan "prefits" for the Mosin-Nagant that are actually fully chambered- meaning the shoulder needs to be set back to establish correct headspace. To get an idea of just how much, I'll add layers of tape to a no-go until I get resistance after screwing on the barrel (just hand tight at this point). This difference to the "go" is approx. how far I need to set it back, and allow a bit for crush.
 
I was able to use it, UNDER the extractor claw [i.o.w., with extractor holding it to the face of bolt], and the straight bolt went in and pivoted from 12 o’clock [up] to between 1 and 2 o’clock [or 45 degrees down], before it stopped. I didn't FORCE it, but brought it to where moderate resistance was felt.
Click to expand...
I can measure the length of the chamber with a field reject length gage. I can measure the length of the chamber with a go-gage length gage and the same for the no go-gage; problem, convincing someone else they can also.

The Mauser bolt advances forward when closed. A reloader can measure the advance In thousands, again there is the problem of convincing someone it can be done.

The difference in length between a go-gage length chamber and a minimum length/full length sized case is .004”, the difference in length between a minimum length sized case and a no go-gage length chamber is .008” and then there is the field length gage. The difference in length between a minimum length/full length sized case and a field gage length chamber is .012” for the 308W.

I suggest you make your mind up about using the filed gage when checking the length of the chamber from the shoulder to the bolt face, the long gage will not allow the bolt to close. But there are methods and techniques when added to a few shop skills that will allow you to determine the length of the chamber with any gage like the go, the no and beyond gage. I make gages that fill in all of the blanks meaning I make gages for short chamber and long chambers, not necessary but I have gages that go from -.012” shorter than go-gage length chamber to infinity; that would be about .016” longer than a go-gage length chamber or .002” longer than a field reject length gage for the 30/06 chamber.

Not all gages are made alike, on the Mauser I would remove the extractor when using a chamber gage.

F. Guffey
 
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