Jim Kobe, your idea sounds like a plan! Rigging a dial indicator solidly to bear on the back of the stripped bolt. I think you wouldn't need the headspace gauges just for checking for setback; just pull backward on the bolt, to insure lug contact as you close it, and you should be able to read the difference, if any, between closing and fully closed positions.

I have a very small mirror which I use to observe lug wear with a small light shined in to reflect the image. One customer of mine had a 98 Mauser in .308 with a heavy barrel in a fancy stock. The mirror trick clearly showed a lot of deformed metal. It swallowed the no go gauge plus I forget how thick a shim; total was about .020" excess headspace if I recall.

Whoever built the gun lapped completely thru the case hardening. I recommended he retire the gun, but he said he would continue to use it with neck sized cases! Hope he's ok.

Safe Shooting Friends. -"gunsmither"

Thank YOU , Jim. Nice technique.I think I will try doing it that way except I will size a case down till it just closes easily. My thinkig is if the chamber is on the deep side but still in tolerance using the go gage would add this depth to whatever the set back was and indicate that set back was greater than actual.

Is all the work necessary to salvage a mod 98 action worth while? I'll forget the 1916 Mauser. roger

Certainly in the wartime M98 ,like my '43 Oberdorf,QC was spotty. The case hardening on my rifle was spotty too. It was lapped then re-case hardened.

Gunsmither

Are you sure you wouldn't need a guage in there. I have many mauser actions here. And if you completely strip the bolt and put it in the receiver on an empty chamber there is quite a bit of movement back and forth once you get the bolt closed.

Moreover, doesn't a go headspace guage assume some headspace, like a few thousandths of an inch or so. Otherwise, one would have to have perfect ammunition that was custom made for a particuar chamber in order for that ammunition to chamber.

So, wouldn't one have to know how much headspace a go guage assumed, and them measure the difference between the bolt puled back and the bolt pushed in against a go guage to know what the headspace was (e.g. what we want to know is the distance between a properly chambered round and the face of the bolt when it is being pulled back against the locking recesses in the receiver).

Blue

Blue, read the blurb two above you roger

blue, you are correct. I was looking at the photo posted by gsp which shows the bright wear area, and I was thinking the bolt bore on the unshiney portion first(left portion of lug in photo) on it's way to closed position (what I thought Jim Kobe referred to as the "high spot"). No way! Please excuse my backwards bolt rotation brain fart! This throws my entire theory out the window. It's my birthday today, and I just turned 54, and I think Alzs is really setting in!

If there is a definite "High Spot" on a particular action, as Jim Kobe says, then my original no gauge needed idea may work to check setback. I've got some actions laying around that I'm going to check.

The dial indicator will show headspace over a "Go" gauge length by pushing bolt forward, indicating any headspace, but it doesn't seem like it will show lug setback unless there is a definite "High Spot" on the lug to reference from.

Interesting thread! Safe Shooting Friends. -"gunsmither"

This is an interesrting subject. I would leave the terms "never" and "always" out on the back porch. My opinion is that the sysem 98 is the best turn bolt design ever conceived. Everything else is a step backward. Having said that, I too have seen setback lugs. In the ones I saw, all were FN actions (Rockwell about 25) using rounds like Super Mashburn Margun and 7x61 Sharp and Hart. Th important part is the action did not fail (as in blow apart) It stretched, and gave until even a moron would know something needs to be looked at. This is precisely the original design concept. Soft inner core, carburized and case hardened outer surfaces. The most dramatic blow up I ever saw was a Browning A-bolt, I've seen 308 Win touched off in a 7mm Rem Mag chamber (Impressive) Shooter was shaken, but not hurt...happened to be a 98 action that appeared serviceable afterwards....so...if you take a 98 and harden the bejesus out it, the "stretch" and "give" will turn into a sudden, dramatic failure. IF re heat treating is on order, pick the guy to do it with great care and make sure carburizing be the order of the day if that was done originally

what Duanae said and then what Parker did...

Ackley took those "dead soft" arisaka actions, and subjected them to pressures that DESTROYED mausers and springfields... the jap actions just gave and stretched, without blowing up...

jeffe

Go back and read the Ackley test. He used an old WW1 vintage M98 that had been butchered, and had a dozen holes in the receiver. I think a VZ-24, or Mark X would be able to take more than the Arisaka.

To sum up:

I don't think anyone here wants to blow up their action. Rather, all people want to know is what is excessive headspace, what causes it, and what can people do to avoid it.

We all know that excessive headspace (incorrect headspace) can be caused by lots of things, of which lug setback, or lug recess setback are two.

What casues it is steel that is soft enough to change dimensionally after repeated firings (or even one firing for that matter). That steel could even be one very small bump on a lug or recess that has not been lapped away, thereby giving a false indication of true headspace. Also, out of round or out of flat surfaces could give false readings, as could measuring devices. Improper machine work could also cause excessive headspace (cutting too deep or cleaning up the bolt face without taking it into account)

What can one do to avoid it.
1. In general, use the weapon for the firing pressures that it was intended for, although that is not a guarentee.
2. Reharden by proper means those areas that may be prone to dimensional change through excess wear or excess pressure.

OR

1. do nothing, accept that it may happen, keep checking to see if and how much, and deal with it when it gets excessive.

Blue