Mosin Headspace Problem

[Hundids]

I recently bought an extremely nice all matching example M91/30 from a Calgunner. The wood, metal, and overall quality is like new for a refurb. It's a fantastic Izhevsk 1933 hex receiver, but there's one problem. It fails a no-go guage, and the bolt closes on the guage like there's nothing even there. After doing a little research, I learned that this can be remedied by simply swapping in a different bolt head. The bolt head replacement just came in todays mail, and it too fails the no-go guage, like there's nothing even there. Is there anything else I can do? The bolt heads cost $25, so it doesn't make sense to keep ordering bolt heads for an eighth of the cost of the rifle. This is the guage I bought http://www.ebay.com/itm/251901703512...%3AMEBIDX%3AIT Any help would be greatly appreciated. Thanks.

[0321jarhead]

You got what you paid for. Do it the right way with a Forster Field Headspace gauge from Brownell's.

319-000-004WB
Field, 7.62x54R Russian
Mfr Part: BG762RF

[NOTABIKER]

I have never had a mosin head space problem. It is checked during referb. Did the past owner say he shot it. If so i doubt it needs fixing. I have owned maybe 25 mosins and shot everyone without checking JACK

[Bainter1212]

I have 4 of them and they all pass nicely. Even if you swap bolts around. Never seen one fail before.
You might want to sell it off and buy another.

[arnie19]

Just fire form the cases to that chamber and don't resize them .Use a neck sizing die .

[Flyin Brian]

OP, first of all, you should check the rifle with a field gauge before changing boltheads. If you only have the NoGo, then maybe you can find someone nearby who has a set you can borrow.

I doubt there is a problem with the gauge you bought. I know the ebay Seller very well and he is a good guy with good morals. If the gauge is somehow defective he would make it right, but without a field gauge you don't know what is wrong yet.

I would advise against getting the Forster gauge that Jarhead linked to, as you would need to remove the extractor from the bolt to use it, which is rather inconvenient on a Mosin, and might end up with a broken extractor.

Good luck- I'm sure there is someone nearby with a field gauge!

[Crunch130]

Unless you plan to shoot reloads, it shouldn't be a problem. And yes, failing a No-Go on a used military rifle is not a problem. That's max headspace for a NEW barrel. A field gauge is the right tool for a used barrel.

Even at that, a bit of excessive headspace is no big deal if you're shooting steel-case ammo. One use, throw it away. Probably not an issue for new brass, either. If you reload, just back off the resizing die to reform the case so it "just" chambers, and now you have custom brass that headspaces off the shoulder rather than the rim (like 8 mm Mauser or 30-06 or 308, which are all rimless).

Crunch

[Hundids]

The rifle was never fired by the original owner. It's an early import. Maybe I should have waited to decosmoline until after I checked the headspace. Don't rifles that fail the no-go guage but pass the field suffer from seriously degraded accuracy? Is there any solid remedy for passing the no-go in a situation like this? I don't reload and wasn't planning on using steel case surplus in this rifle. Maybe that's why they sold it in the first place.

[Bainter1212]

The rifle was never fired by the original owner. It's an early import. Maybe I should have waited to decosmoline until after I checked the headspace. Don't rifles that fail the no-go guage but pass the field suffer from seriously degraded accuracy? Is there any solid remedy for passing the no-go in a situation like this? I don't reload and wasn't planning on using steel case surplus in this rifle. Maybe that's why they sold it in the first place.

The only remedy is to remove the barrel, set back the barrel shank a thread and recut the chamber. Not worth it unless your best bud is a gunsmith.
Accuracy may or may NOT suffer. Only bench shooting will determine that. I have seen MNs with bores that look like the surface of the Moon shoot very well, and others with pristine bores shoot awful. Only testing will tell.
Shoot the thing. If accuracy is acceptable and your case heads don't seperate, fuggetaboutit and keep the thing.

[Enfield47]

The rifle was never fired by the original owner. It's an early import. Maybe I should have waited to decosmoline until after I checked the headspace. Don't rifles that fail the no-go guage but pass the field suffer from seriously degraded accuracy? Is there any solid remedy for passing the no-go in a situation like this? I don't reload and wasn't planning on using steel case surplus in this rifle. Maybe that's why they sold it in the first place.

Nope, not necessarily. Accuracy problems are usually linked to a shot out bore more often than headspace. Enfield's that are well broken in can be notorious for closing on a SAAMI field gauge but still be good shooters. The military field gauges are a little longer and allowed the barrels to keep from being replaced too soon.

The Mosin has a very strong action so you should be fine firing it. I would take it to the range and see how well it shoots before ordering more parts or doing anything drastic.

[OniKoroshi]

I would double check the gauge measurement and make sure they didn't send you a different gauge.

[adamjay]

Fwiw, I use Okie Headspace gauges, as do many collectors whose experience dwarfs mine. They are built with a notch for the extractor, so you don't have to do anything but slip em in and close the bolt. Highly regarded in many collector communities.

I posted on another forum, asking about gauge thickness, and the owner of Okie Gauges piped right in with these numbers, which I thought was a pretty cool move (I assume he won't mind me re posting)


Field gauge 0.076"
NoGo gauge 0.073"
Go gauge 0.064"
Gauge diameter 0.562"
Firing pin clearance 11/64"
Extractor notch 1/4" x 0.180"

I hold my thickness dimensions to +/- 0.0005"



I suppose you could measure the gauge you bought to see if it is close to these numbers.

I have heard many discussions on the fact that there is definate variance across different companies' go, no-go, and field gauge thicknesses - that you should not mix sets because of "stacking tolerances". (Not sure what exactly that's supposed to mean, but I've heard it a few times).

I have buddies who have never checked headspace on their Mosins- ever!
These are the sometimes the same guys who chuckle when gasses spray them in the face.
Me, I've always been a bit more conservative.

[Patric78]

Hello Hundids, this is Patrick, uofmdaddy78, I am the maker of the gauge you are using. My good friend advised me of the issue you are having. I'd like to firstly remind you that when you bought my gauge, you also received my word that I would gladly stand behind the craftsmanship of the gauge as well, I'd like to offer you a Field Gauge, free of charge, but I would like to get a hands on of this suspect gauge. If you would kindly go to your eBay account and send me a message with your address I'll gladly send another NOGO and FIELD. Along with a self addressed stamped envelope for the return of the one you have.

As far as the gauge is concerned. Manufacturing errors can happen, though extremely rare, the likelihood of the gauge being off more than .002 in any spot is a long shot. However if an error was made I'll gladly report back asap that finding.

As far as the mosin is concerned, new looking from the crate does not mean properly assembled with parts that pass a headspace check. Very rare, but at least six separate occasions in the 1000+ sets I've sold, have customers found a fresh from the crate 9130 or m39 with too little or excessive headspace.... All were remedied with bolt head swaps with guns they already had. One fellow had three heads swapping back and forth until all were between GO and NOGO.
With that unfortunately mosin bolt heads are not numbered like the 303 bolt heads are... So you are literally playing a crap shoot to find a bolt head that is in tolerance, especially if there's another issue, possibly in the locking lugs or chamber lip.

I sincerely hope to help you get to the very bottom of your issue on this gun, even if proven to be my error.
I surely appreciate the opportunity to make good on the guarantee of craftsmanship that I afforded you when you purchased my gauge.

Stay safe and Thank You!
-Patrick

[Flyin Brian]

Awesome!! I knew the OP would find a field gauge close by. I didn't realize it was going to be found in his mailbox though

Nice gesture, Patrick. And welcome to Calguns!!

[adamjay]

Kudos, Patrick! That's some old school customer service right there. Welcome to the forums.