Mosin-Nagant question

[NOTPARS]

Last Decmember I picked up a Mosin-Nagan 91/30 from S.O.G. Not only was it numbers matching, its in excellent shape. No scratches, rust, and the bore looks brand new. The tag says it should be inspected before firing. Someone at the gunshow told me to check the headspace. I am new at this and asked around. I was told there are probably not many gunstores (Kansas City area) that can check the headspace. What should I do to ensure the rifle is safe to fire? I had one gunsmith look at it and he said it operates like a brand new rifle. Looks brand new too.

[WiK]

Ok, if this were mine, I would not bother if it were all matching. I have not even heard of anyone getting one with bad headspace. I have a go and no-go and almost feel it was a waste of money as all of my Mosins were in spec.

If you feel you have to check the headspace, then just order a gauge from some place like Brownells and check it yourself. I put a notch in mine so that they clear the extractor. It was much easier then taking the extractor out.

Check in the C&R forums as there is a Mosin section there for more questions.

[NOTPARS]

Thanks for the reply. Yep, the serial number on the barrel, bolt, magazine box, receiver, and butt plate all match. It is supposed to be unissued and boy is it pretty.

[WiK]

My first two Mosins were still in the wrap. I did not have gauges at that time to check the head space. One bolt was matching the other was a force match. I did take the first shot at the hip with my head turned and inspected the shell after.

[Disgruntled Computer Tech]

What, exactly, is checking the headspace? I just bought a 91/30 and the numbers on the bolt and barrel match. Should I worry? :)

[Noah Zark]

Originally posted by Disgruntled Computer Tech
What, exactly, is checking the headspace? I just bought a 91/30 and the numbers on the bolt and barrel match. Should I worry? :)

Headspace is the distance from the boltface to where ever the cartridge is supported by the chamber. On a rimless cartridge like the 308, the case is supported on the shoulder, the tapered section where the body necks down to the bullet diameter. The actual point (ring) of contact is tough to define on two conical surfaces of just slightly different diameters.

On your 7.62x54R, the cartridge "headspaces on the rim", which means that the critical dimension is between the boltface and the rear face of the chamber between which the case rim rests when a round is chambered. In the Mosin, if there is insufficient headspace, (gap too tight) the bolt may not close on the cartridge. If there is excessive headspace, the cartridge will be free to move fore-and-aft, and the danger here is that some of the firing pin strike energy may be expended in shoving the case forward, resulting in erratic ignition.

I have a Go and No Go gage for the 7.62x54R and have checked perhaps 25 or 30 rifles and only one passed a No Go. That said, I still bought it and shoot it, since it was "excessive" by about only 0.004", determined by shimming the No Go gage.

With Mosins, I would be more concerned that the firing pin projection is set correctly so that primers are not pierced.

Noah

[Disgruntled Computer Tech]

Wow, thanks for the info! :p :)

[jmehrten]

All mosin parts are suppsed to be interchangeable. It was part of the Tssar's and later the Soviet specification for the rifle. All have very good metal, and don't seem to suffer lug setback even when exposed to the worst milsurp. Never heard of one with bad headspace.