Odd bolt issue on Mosin - Help?

[penguinofsleep]

Was hoping someone may be able to help me with an odd issue I'm seeing on a Mosin:

Right now, when I have a round chambered, the bolt won't shut if its the last round or the first round (of all 5).

- Gun works perfectly with 2, 3, or 4 rounds in the gun. If it matters, when I empty all the ammo out, the bolt is very smooth, especially for a Mosin. Gun goes bang with no issues at all on these rounds.
- All matching serial numbers. Have already taken it apart (completely) and gotten all the cosmo out.
- It is smooth right until it suddenly gets stuck before closing. Happens with the bolt is about 20 degrees away from closing. This is a standard M91 where the bolt sticks sideways when closed.
- If I drop a round into the chamber directly (by pass internal magazine), the bolt gets stuck as well.
- Didn't notice anything unusual in the primer strikes.
- Tried swapping rounds out in case those two happened to be out of spec. Didn't help. Swapped out rounds didn't seem to have anything wrong with them.
- This is only happening with one of my Mosins, not both. I took the bolt/group out and double checked, couldn't find anything wrong. Figured if I put one together wrong, I would have put both of them together wrong since I put them together following parallel steps (ie insert firing pin + spring on one, then insert on other before moving to the next step)

Thanks in advance.

[SKSer45]

sounds like you got some cosmo stuck in there somewhere....or just need to lube the entire bolt with some rem oil...all else fail just buy a new mosin

[Chaos47]

What do you mean wont shut?
What stage is it stopping?

You can't even get the bolt to move forward?
OR
You can't get it to lock shut?

[penguinofsleep]

It won't lock shut.

I am not sure what you are referring to by stage, but I can extract a round after firing, push forward on the bolt to chamber the next round, turn the bolt down, and when the bolt is at about 20 degrees, it stops closing if its the first/last round.

[Flyin Brian]

I would bet the problem is the extractor. Pull the bolt out, hook a round under the extractor lip and snap it in place onto the bolt head. Now slide the whole assembly back into the rifle and see if the bolt closes easily. If it does, your extractor is bent or has a burr on the face of it, or you have crud impacted into the extractor cut on the breech of the barrel.

Of course, only do this if you have some dummy rounds, snap caps, or you are at the range with the muzzle pointing down range. Don't be loading live rounds at home.

[penguinofsleep]

thanks. ill try that when i get the chance to do it safely - i wouldn't do this at home w/ a problem gun either. however, is there a reason this won't happen on every round?

one question though, when you say extractor, you mean the silver colored extractor on the bolt/bolt face, not the extractor in the gun (the black colored hook shaped part that knocks the empty shell out)? - sorry if this is silly, im not very familiar with all the terminology sometimes.

[Fate]

Yes, the extractor on the bolt. Mosins don't work without feeding a round from the magazine. Dropping one into the chamber won't work because the extractor won't pop over the rimmed round. That's why it must come from the magazine. You also might have a compound problem of extractor AND a bad interruptor or magazine follower spring (the first/last round issues point to a poorly functioning interruptor or a weak magazine follower spring.

Try swapping parts with your Mosin that works to narrow down possibilities. You can even swap the bolts for this function test (headspacing is almost never an issue with Mosin Nagants).

[Turo]

thanks. ill try that when i get the chance to do it safely - i wouldn't do this at home w/ a problem gun either. however, is there a reason this won't happen on every round?

one question though, when you say extractor, you mean the silver colored extractor on the bolt/bolt face, not the extractor in the gun (the black colored hook shaped part that knocks the empty shell out)? - sorry if this is silly, im not very familiar with all the terminology sometimes.

Just as an FYI, the extractor is the part on the bolt that hooks the rim and pulls the case out of the chamber. The ejector is the blued part of the receiver that pushes on the back of the casing to make the casing rotate out of the gun when the bolt is pulled to the rear.

Brian is talking about the extractor.

[Flyin Brian]

Yes, the extractor on the bolt. Mosins don't work without feeding a round from the magazine. Dropping one into the chamber won't work because the extractor won't pop over the rimmed round. That's why it must come from the magazine. You also might have a compound problem of extractor AND a bad interruptor or magazine follower spring (the first/last round issues point to a poorly functioning interruptor or a weak magazine follower spring.

Try swapping parts with your Mosin that works to narrow down possibilities. You can even swap the bolts for this function test (headspacing is almost never an issue with Mosin Nagants).

after the round has been chambered, so it really makes no difference how it got there, by either single feeding one by one or from the magazine.

[BigRig81]

I can't find the video now, but I saw a guy showing this exact problem and it was a bent extractor. But he couldn't close it with any amount of rounds, wierd that you are having this problem with only certain amounts.


take out the marked piece and try to close the bolt, could be your problem.

[Fate]

Yes, the extractor on the bolt. Mosins don't work without feeding a round from the magazine. Dropping one into the chamber won't work because the extractor won't pop over the rimmed round. That's why it must come from the magazine. You also might have a compound problem of extractor AND a bad interruptor or magazine follower spring (the first/last round issues point to a poorly functioning interruptor or a weak magazine follower spring.

Try swapping parts with your Mosin that works to narrow down possibilities. You can even swap the bolts for this function test (headspacing is almost never an issue with Mosin Nagants).

after the round has been chambered, so it really makes no difference how it got there, by either single feeding one by one or from the magazine.

Brian, you're right. I was wrong about when the extractor connects to the bolt.

I will restate/clarify my earlier statement in that a round just dropped into the action (but not fed into chamber) won't feed. It has to be at least pushed beneath the EJECTOR. This holds the round to be fed at the proper angle so it will chamber. If it's not being fed from this spot, the nose of the bullet will hang and the round won't chamber and the bolt won't close.

It has been awhile since I closely looked at the process so I dug out one of my rifles and tried to figure out what would make the first and last round fail to feed.

The only thing I can see that affects 1st and 5th round would be that they aren't being pushed past the interruptor by another round into the spot held by the ejector. The first round starts there, the 5th is pushed into position by the magazine follower. So either the ejector or interruptor (or both) could be contributing to problems with rounds 1 and 5. Still...it's odd that it is the bolt that isn't fully locking for those rounds. I've not figured out how the ejector or interruptor would prevent the bolt from rotating the last few degrees.

[penguinofsleep]

thanks for all the ideas so far. keep them coming

also seems like there are a few different ideas going around right now... so now i at least have the peace of mind that i wasn't just making a mistake or crazy.

for the magazine spring, i did notice that it was a little bit looser on the one where the bolt can't close, but i didn't see how the two could affect each other mechanically since it seems like the bolt closing has nothing to do with the magazine (or its contents).

[Josh Smith]

Hello,

I would like to see a movie of it.

My bet is that, if it's always the first and last rounds, then those rounds are getting pushed out of round. The symptom you describe is consistent with a bullet leaning over a bit.

When loaded singly (using the push feed system - yay!) do you ever experience this?

If you would like, I'll load up five DUMMY rounds (no primers, and I'll drill the cases) and send them do you. Cycle them through your rifle and send them back. I'll break out the micrometers and other measuring devices I have laying around here and see what's going on.

Brass cases will tell the story much better than steel.

Regards,

Josh
wabatuckian@gmail.com
or
PM me here.

[Vlad 11]

http://www.surplusrifleforum.com/viewtopic.php?f=28&t=48259

[penguinofsleep]

thanks guys! i won't be able to post a video right now - again this is not something I want to demo with live ammo at home. hopefully i will have time to go to the range this week...

josh smith i am PMing you right now.

edit:

I can't find the video now, but I saw a guy showing this exact problem and it was a bent extractor. But he couldn't close it with any amount of rounds, wierd that you are having this problem with only certain amounts.

Both of my bolts and extractors look like the one in the above image. However, I imagine that if one worked or failed, the other would do the same. Also, I tried looking around for pictures of a "proper" mosin extractor just now and the few pictures I found seem like they are all a little bit bent at that point (no idea if I was looking at more problem extractors though).

Pictures to come soon.