mosin nagant headspace

[scotsman]

I bought two 1891/30 rifles yesterday just because I thought they were cheap. Took them apart cleaned them and they look good to me. 1940 date on one and 1942 on the other. How important is it to buy gauges and check headspace before firing? I just hate to spend half the cost of one of them for gauges that I will never use again.

[parkergunshop]

Simply fire a round in each rifle.  and compare the brass to an unfired round, there should be no primer protusion or ring marks ahead of the solid base of the case.
Since the 7.62 Russ is a rimmed round you are less likely to see headspace issues

The likehood of excess headspace is very slim with the M-N Rifle

[mauserand9mm]

Protruding primers is more a sign of low pressure and excessive headspace in a rimmed cartridge only, so it may not show up as a backed out primer. A shiny ring above the solid web is a good indication of excessive headspace but may not be an issue if you only fire the cases once. If you reload you may want to have good headspace but there are other ways to extend case life if you don't.

A complete head separation is the ultimate sign of excessive headspace. Headspace issues are somewhat over-rated. Head separations do lead to blowback towards the shooters face but a Mauser 98 shroud, for example, blocks the direct path of gas. I'm not sure what the MNs have in this regard. A pierced primer is a more serious issue but, fortunatley, very uncommon. I have had a few head separations over the years and have not noticed all of them at the time of firing. (I've also used steel cased ex-mil 8mm ammo that sometimes doesn't expand to fill the chamber properly and gives me blow back.)

I usually just fire the rifle and see what the case looks like. Always wear shooting glasses! Some others will put the rifle behind a tree and rig a remote trigger release (ie string) but I think this is overly cautious.

[Mikey]

One thought to consider is that with most military bolt rifles you may encounter generous chambers and long throats which may lead one to think their rifle suffers excess headspace when they might not.  If you intend to reload you may wish to also consider neck sizing your brass only for longer brass life.  This is a common situation with the 303 British rifles and reloading brass was not a wartime consideration but the need for positive feeding and chambering was, hence the 'roomier' chambers. 

[scotsman]

Thanks for the replies I will fire them and compare the brass to unfired rounds. I don't intend to reload for them, just buy a batch of surplus ammo and play with them. Again thanks for the help.

[parkergunshop]

Scotsman,

Good deal,  one of the advantages of the rimmed case is that you can have generous chambers that allow for easier chambering of rounds when there is a build up burnt power or even a little dirt in the chamber.   Even if your cases stretch on firing, that does not necessarily mean that the headspace is excessive since the headspace is on the rim not on the shoulder of the case.

The only advantage for rimless cases is in the area of feeding a little better, headspace and sealing of the chambers are negatives for rimless cases that have to be dealed with.   Remington deals with this sealing of the chamber by enclosing the bolt nose into the barrel recess which is an advantage with rimless cases, but unnecessary with the H&H case which seals the rear of the chamber like a rimmed case.

The Rimmed and H&H case designs are better for high pressure loading for this reason.

[Rex in OTZ]

They sell small wafer type head space gages, even heard of guys cutting up feeler gages to fit in there as a gage,
if you do follow the instructioins.

The great part about a Mosin is you can swap bolt heads if headspace is off, they made 3 diffrent bolt head thicknesses.

http://www.surplusrifle.com/shooting/headspace/index.asp\

I have a odd way I check head space if its adiquate or not, its quick, its easy, not exact, but good enough to tell you if you  your looking at a unsafe rifle or not.

[parkergunshop]

Rex in OTZ wrote:

 Rex in OTZ
« on: Today at 02:56:47 PM » Insert Quote

They sell small wafer type head space gages, even heard of guys cutting up feeler gages to fit in there as a gage,
if you do follow the instructioins.

I have cut a small piece from a .005 feeler guage and used it between the case head and the bolt face.   If the bolt will not close then the headspace is not excessive.  This works with all case types rimless, rimmed and belted.

I only purchased, 30-06 and H&H go and no go guages use the .005 shim for the rest without a problem.

This works with control feed actions like Mausers, Springfields, Endfields, pre64 Model 70's.

[mauserand9mm]

The only thing with wafers is that you have to know the thickness of the case rim to make a proper assessment of the headspace but it is a good indication of how much space there is with that make of case/ammo.