Mosin Nagant headspace.


August 21, 2009, 03:24 PM
Hello all.

I got a 1934 Mosin Nagant M91/30 and the deal is when I put a round (live or spent casing) in the chamber the bolt is a mother to close.

If the chamber is empty the bolt open and closes no problem.

There are no burrs in the chamber and the rounds do not stick in the chamber as well. When I put a round in the chamber and not close the bolt the round slides right out and a spent casing comes out with a very light tap from a cleaning rod.

This sounds like a headspace issue. Is there a way to adjust headspace on the Mosin Nagant?

Any thoughts?


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August 21, 2009, 03:32 PM
Or it could have some dried, hardened cosmoline still in the locking lug recesses in the receiver. My friend just received a 91/30 where the bolt is hard to close while chambering a round but easy without just as you described. HE cleaned the exterior well, but had no way to inspect or give the chamber as good of attention so he ran into this issue. After the application of some harsh solvent (brake cleaner) and working the action a bunch wiht a spent casing, it loosened up the cemented in cosmo and the action ran fine after that. See if you might be experiencing the same issue.

August 21, 2009, 03:46 PM
How does one clean the locking lug recesses of the receiver?

I use a 12ga bore brush to clean the chamber(does a good job).

Should I spray some carburetor cleaner around the chamber and let it soak?


August 21, 2009, 04:30 PM
I have this same problem with mine, although ive cleaned it like crazy. in fact, last time i shot it, i had to pound the bolt handle with a lead hammer to get it loose

August 21, 2009, 06:05 PM
There is also the issue of "sticky bolt syndrome" that can arise when using lacquer coated ammo. After shooting a number of rounds, the gun heats up to the point that it softens the lacquer coating on the shells and this goo is transferred to the bolt mechanism as you feed and eject the cartridges. The sticky stuff then begins to bind up the action as it dries thus making the bolt action get more difficult as you continue shooting. You can alleviate this with a thorough cleaning after you shoot or just avoid it altogether by using brass or copper coated shells rather than the lacquer coated ones.

This is different than the OP's issue i think. In his case, its probably just some cosmo in the lug recesses creating a tolerance issue. Since getting in there with brushes i kinda difficult, chemicals, brushing as best you can with an old toothbush and repeatedly working the bolt with the chemicals soaking in is a good start. Eventually it should grind away that old cosmo.

August 22, 2009, 08:54 AM
The phenomenon of dried cosmoline in every crevice is your likely culprit. I have found that patience and Kroil penetrating oil does a pretty good job of getting in the locking lug recesses.

Remove the action from the stock and squirt some up in the locking lug recess and rotate the action around so that the penetrating oil liberally coats all the areas in there. If you can get in there with some patches cut from burlap or similar with an abrasive finish you can get a lot of the stuff out of there.

Same for cosmoline in the chamber. Take a 30-06 or 308 chamber brush with you to the range and a couple of mops. Fire the rifle until it gets sticky bolt syndrome, then use Kroil on your bore brush and give it a good scrubbing. Mop out the residue. Fire until it gets sticky again, and repeat.

I've found that about 5 cycles of firing and cleaning and the rifle stops with the sticky action problems.


August 22, 2009, 09:09 AM
Take a 45 cal bore brush a segment of on of those 3 piece cleaning rods and chuck it up into a cordless drill. Use liberal abounts of #9 and clean out the chamber.

August 22, 2009, 09:26 AM
Things to do when encounter bolt problems on a mosin (hard to chamber or extract)
1. Too tight action screws. Loosen these two screws and then retighten them equally. Bedding the stock at these two contact points has helped dramatically in some cases.
2. Clean the bolt thoroughly.
3. Clean the chamber thoroughly as described above.
4. Look at your ammo. Some ammo, such as Albanian, have greatly varying rim thickness.
5. Headspace - have it checked. Out of my 30 mosins, none have headspace problems so I think this is somewhat rare.

August 25, 2009, 12:57 PM

After taking the gun to the range and putting about 80 rounds the stickiness has disappeared.

Thanks for everyone's input.

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