Chewed up bolt

[Earle]

Recently bought a Brno ZKK 602 in 375HH, and the rifle itself is in exceptional condition. The bolt however, looks like it was abused. See pics. It binds up tightly when operated at less than warp speed. At first i thot maybe it was not the original bolt, but the numbers match. My question is, can i do anything to slick it up and polish the scratch's, or is this something a qualified gun smith should look at? Also, anybody got any idea's as to what would cause these markings? Any info is appreciated as i am clueless, never having seen this before.

 

[JimP]

Polishing the bolt shouldn't cause any problems but stay away from the locking lugs. They are what make the bolt secure when a round is chambered.

I can't seen just how deep the scratches are but you can try some automotive polish compound that removes the scratches in the paint on them and see what happens. If they are deeper you can also use some valve grind compound and then finish it off with the automotive polish compound.

 

[Ike85123]

I have a friend that stored 2 bolts in a royal crown bag in his rifle case for a trip. His looked the same.

 

[Earle]

The pics don't really show the marks all that well. The bolt body appears "scuffed", like it was forced thru a tight receiver. Not scratched, but (rubbed) scuffed. The extractor on the other hand is heavily scratched, almost like it was forcefully pried, several times with something pointed. It's the extractor that has me baffled, more so than the bolt body.

 

[Hogpatrol]

There may be some obstructive grit where the lugs contact receiver body (lug abutments). I would get the tool that's made to do that job and give it a good cleaning. Light polishing can be done with a green scotch brite pad. If unfamiliar on cleaning the lug contact surfaces, the short video in this link shows how.

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[Sarg]

I would guess that it has had a replacement extractor fitted poorly or by a Nincompoop ?

Can make all the difference on a Mauser, you could remove it & holding spring/collar, see if that makes it run smooth, then you know what to look at ?

 

[Hunter4752001]

I think much of the problem could be rectified by careful cleaning and then polishing of the extractor and the bolt. However there may be some things best left alone and other issues you (and I) don't have the training or experience to identify. Both the 602 and the CZ550 are now out of production so getting a new extractor or bolt could be problematic. I would err on the side of caution and get it checked by a good quality smith. Not worth doing a bubba job on something that may be difficult to replace. After all, paying for a top class job beats pointing a jammed rifle at something big, hairy and angry.

 

[fourfive8]

Kind of hard to see the details but the scuffs or scratches by themselves wouldn't worry me too much. But how they got there has me wondering. You'd have to go to some trouble to put scuffs like that on different parts of the bolt through even rough use in gritty conditions- those marks go beyond that IMO. Scratches, scuffs and the like won't be the cause for any strength or safety issues. But why would the bolt have such marks? Could the rifle have experienced a high pressure event requiring force to open and remove the bolt? Was the damage to the bolt caused by an over pressure event along with the subsequent force used to open the action up?

A large concern would be a high pressure event compromising lug strength. Mangling the extractor or groove would not necessarily cause a strength concern but more likely lead to a functionality issue. It looks to me like the extractor has been forced out of its groove in the bolt body. That could be caused by someone forcing the extractor out of the groove without taking into account the undercut design in the groove. OR, and this may be the kicker, and a good reason for a gunsmith to look at it... this damage could have been caused by gas from a ruptured case and/or an over pressure event.

I've added a pic of a ZKK 602 375 bolt from my rifle that has approx. 100 rounds fired through it. The line points to the area of my concern with the extractor groove in the damaged bolt. Additionally that damaged area is where the extractor is in the groove when the bolt is in full battery and ready to fire. I took the liberty of adding a segment of the pic of the OP's bolt for comparison.

 

[Earle]

Thanks for all the replies. Got me thinking that maybe a smith should have have a look at the gun. Pulled the bolt apart and found a ton of hardened goop built up on the underside of the extractor. That plus the weird scratch's running in every direction make me think a pro should have a look.

 

[fourfive8]

Good plan! Also have the headspace checked.