Bolt has forward play when closed

NightOwl07

NightOwl07

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Hi guys,

Ran into an unusual problem today. Have a Zastava M85 in 7.62x39 that saw about 200 rounds of norinco surplus down the barrel.

Noticed today that when the bolt is closed and the striker released (dry fire) without a casing in the chamber the bolt can be wiggled forward and back by about 1mm with the bolt handle still down. It is solid if there is a fired cartridge in there.

Is this a sign that the lugs are worn in some way? Is this a safety issue?

Thanks in advance,
Dan
 
My M85 has over 1300 shots through it of Chinese non-corrosive, Barnaul, Sellier and Bellot and Tula ammo and the bolt after dry firing does not wiggle at all. It's stiff like a rock. What you are experiencing is weird. I can't believe that the lugs would be worn out after 200 shots. Did you ever disassembled the bolt and perhaps assembled it in a wrong way?
 
It's strange to me too.

I have disassembled the bolt yes, however the lugs are one piece with the sleeve and it's the entire sleeve that moves, not just the handle/cocking piece.

I just noticed it today which meant I probably put at least 50 rounds or so down range with it doing this...... maybe it's completely fine? Or am I playing Russian roulette here?
 
NightOwl07 said:
It's strange to me too.
I have disassembled the bolt yes, however the lugs are one piece with the sleeve and it's the entire sleeve that moves, not just the handle/cocking piece.
I just noticed it today which meant I probably put at least 50 rounds or so down range with it doing this...... maybe it's completely fine? Or am I playing Russian roulette here?
Click to expand...

The sleeve moves?? That's really strange. There are a couple of videos below showing the bolt disassembly and other issues with the M85 so you can watch them. Could be of some help.
https://www.youtube.com/watch?v=RXLWFKabs9U
https://www.youtube.com/watch?v=EEq3WZStHQY
 
Thanks for the reassurance.

I've not hand many other rifles do this. Is this a matter of perhaps 7.62x39 having somewhat more generous tolerance to work with surplus ammo or just a fit and finish thing?
 
NightOwl07 said:
Thanks for the reassurance.
I've not hand many other rifles do this. Is this a matter of perhaps 7.62x39 having somewhat more generous tolerance to work with surplus ammo or just a fit and finish thing?
Click to expand...

Don't be so reassured with that "bolt nose clearance". I've handled a few M85's and I've never seen a bolt sleeve moving back and forth on those rifles. From the construction of the bolt it's hard to imagine how the sleeve could move 1 mm back and forth. Check again that you assembled your bolt properly.
You also mentioned that you shot Norinco surplus. Was that non-corrosive or corrosive?
Finally, where did you get your M85 from? Is it a brand new rifle from a dealer or what?
 
With the possible exception on specially fitted match rifles, all bolt action rifles will have some clearance between the bolt face and the face of the barrel.

If the bolt was not assembled correctly, you would not be able to turn the bolt handle down to chamber the cartridge.

Ted
 
It is corrosive, I do a water flush after each range session followed by usual cleaning. There's not a spot of rust on it anywhere. It was a brand new rifle from TradeEx.

There is absolutely no chance that it was from improper bolt assembly. The components that are moving cannot be disassembled since it is one single machined piece along with the lugs. Not to mention that there aren't a lot of ways you can put a mauser type bolt together wrong and still have it fit.

I suppose the source of risk would be if the play is the bolt moving rearward excessively, I'll see if I can get the headspace checked. If it's just some extra space forward of the lugs/bolt nose it wouldn't be an issue when the cartridge is in place since it doesn't headspace at the rim.

If anyone is in the city with a go/no-go gauge for this caliber I'd appreciate it.
 
NightOwl07 said:
It is corrosive, I do a water flush after each range session followed by usual cleaning. There's not a spot of rust on it anywhere. It was a brand new rifle from TradeEx.
There is absolutely no chance that it was from improper bolt assembly. The components that are moving cannot be disassembled since it is one single machined piece along with the lugs. Not to mention that there aren't a lot of ways you can put a mauser type bolt together wrong and still have it fit.
I suppose the source of risk would be if the play is the bolt moving rearward excessively, I'll see if I can get the headspace checked. If it's just some extra space forward of the lugs/bolt nose it wouldn't be an issue when the cartridge is in place since it doesn't headspace at the rim.
If anyone is in the city with a go/no-go gauge for this caliber I'd appreciate it.
Click to expand...

O.K. You used corrosive ammo. There is a remote likelihood that the grooves for lugs in the barrel chamber are corroded to some extent although after 200 corrosive rounds it doesn't look very likely to me. But who knows? On a number of occasions the grooves are neglected during cleaning and I've seen corrosion there in some rifles. Personally, I always use full strength Ballistol and hard bristle brush to clean thoroughly inside the grooves.
Exactly speaking the M85 bolt is not a real Mauser bolt. The Mauser bolt is a controlled feed action and the M85 is a simple push feed action. On top of it, the Serbs slightly changed the design of the M85 bolt some years ago. This is mentioned in that video:https://www.youtube.com/watch?v=EEq3WZStHQY.
Surely, check the head space. Very important.
 
05RAV said:
O.K. You used corrosive ammo. There is a remote likelihood that the grooves for lugs in the barrel chamber are corroded to some extent although after 200 corrosive rounds it doesn't look very likely to me. But who knows? On a number of occasions the grooves are neglected during cleaning and I've seen corrosion there in some rifles. Personally, I always use full strength Ballistol and hard bristle brush to clean thoroughly inside the grooves.
Exactly speaking the M85 bolt is not a real Mauser bolt. The Mauser bolt is a controlled feed action and the M85 is a simple push feed action. On top of it, the Serbs slightly changed the design of the M85 bolt some years ago. This is mentioned in that video:https://www.youtube.com/watch?v=EEq3WZStHQY.
Surely, check the head space. Very important.
Click to expand...

Had a look with a basic bore scope, they're clean.

I understand M85 is not a mauser bolt, I said a mauser type, the point being that the bolt head, lugs, and most of the bolt body forward of the cocking handle are one piece machined steel unlike some other designs we have. This eliminates bolt assembly as a potential cause due to there being no part that can be disassembled in the forward portion of the bolt aside from the extractor.
 
NightOwl07 said:
Had a look with a basic bore scope, they're clean.
I understand M85 is not a mauser bolt, I said a mauser type, the point being that the bolt head, lugs, and most of the bolt body forward of the cocking handle are one piece machined steel unlike some other designs we have. This eliminates bolt assembly as a potential cause due to there being no part that can be disassembled in the forward portion of the bolt aside from the extractor.
Click to expand...

So, any corrosion problems within the locking lug grooves and their worn out are essentially eliminated. However, I still don't understand how the bolt sleeve could have a play forward after being properly assembled. The bolt sleeve /hammer/firing pin unit is screwed into the bolt which, as you correctly say, is one machined piece. Both parts are threaded so after complete screwed them together, there shouldn't be any possible movement of the bolt sleeve. They must be very tight together unless the bolt sleeve /hammer/firing pin unit is not completely screwed into the bolt.
There is also another thing with a "mini Mauser" bolt assembly. If the pin on the guide rib on the side of the bolt which is an independent part rotating on the bolt, is lost like in this videos: https://www.youtube.com/watch?v=RXLWFKabs9U / https://www.youtube.com/watch?v=UYv-mvMiUZw then the guide rib can move freely back and forth. Did you check if that pin is still sitting in your bolt?
 
05RAV said:
So, any corrosion problems within the locking lug grooves and their worn out are essentially eliminated. However, I still don't understand how the bolt sleeve could have a play forward after being properly assembled. The bolt sleeve /hammer/firing pin unit is screwed into the bolt which, as you correctly say, is one machined piece. Both parts are threaded so after complete screwed them together, there shouldn't be any possible movement of the bolt sleeve. They must be very tight together unless the bolt sleeve /hammer/firing pin unit is not completely screwed into the bolt.
There is also another thing with a "mini Mauser" bolt assembly. If the pin on the guide rib on the side of the bolt which is an independent part rotating on the bolt, is lost like in this videos: https://www.youtube.com/watch?v=RXLWFKabs9U / https://www.youtube.com/watch?v=UYv-mvMiUZw then the guide rib can move freely back and forth. Did you check if that pin is still sitting in your bolt?
Click to expand...

I think by "bolt sleeve" the op meant the bolt body. I could be wrong but I think he's saying the whole bolt body can move forward a bit, which is normal.
 
jbmauser said:
I think by "bolt sleeve" the op meant the bolt body. I could be wrong but I think he's saying the whole bolt body can move forward a bit, which is normal.
Click to expand...
No, the bolt body cannot move forward at all separately. You don't know how the M85 bolt assembly works. The bolt sleeve /hammer/firing pin unit (it's like a whole unit) is screwed into the bolt body. The hollow bolt body has a thread inside and the bolt sleeve /hammer/firing pin unit has a thread outside. Both threads engage each other and ditto the bolt body cannot move at all. The first hypothesis that the bolt body could move would be worn out threads but that's impossible on a brand new rifle. The second hypothesis is that the bolt sleeve /hammer/firing pin unit is not fully screwed into the bolt. I checked it on my M85 and it is remotely possible (if a newbie does that). The third hypothesis is that what is really moving is not a bolt body but the guide rib on the bolt body which has missing a set up pin (see#17).
 
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