Brno 600 bolt face not square

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Cleoo1

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I acquired a Brno 600 ZKK that has been modified to 9.3x64 Brenneke. The bolt face was machined for the larger case size. When inspecting the bolt it is not square across the face.
Will this affect the safe operation of the firearm? I have verified the headspace with PTG Go/No go gauges and it checked out OK.
I have fired it at the range one occasion for load testing and had difficulty pulling the bolt back out of the chamber on some cases.
What is the best procedure to remedy this to get the bolt face square? Is there a source for spare Brno bolts or can the bolt face be welded and machined square again?
 
Some Mauser smiths have a bolt face lapping tool. I sold mine years ago. The barrel is removed, a stub holding the lapping tool is screwed into the threads and the lap spun against a closed bolt. The bolt can be removed for inspection. When the lapping looks even, the face is square.

This doesn't matter much if you shoot only factory ammo but if shooting hot reloads it may make a difference.
 
Thanks Dennis for the response. On closer inspection with the bolt removed and a case sitting on the bolt face there is a significant amount of gap on the one side of the bolt, as much as 1/32" or more. The bolt face appears very rough on that side as well. Picture attached.
I am thinking that this might require a lathe to be trued up. Will taking off this much affect the function of the extractor by making the case looser?
 
I don't know how you would go about accurately measuring how off the face is... 1/32 is 31 thou and that is a lot... I guess if you want to spend the money and can find someone capable of doing it, you could have the bolt face recessed and a 'washer' or 'spacer' soldered in place back to the correct dimensions.

That is one ugly bolt...
 
The 1/32" was a rough estimate ... hard to tell for sure but when resting a new case on the true portion of the face there was a significant gap on the other side.
I assume that when soldering a spacer on the bolt that the lower heat level does not change the hardness of the bolt? Any estimate on the hours and cost for that procedure?
 
You could either leave it or throw the bolt out and find another and have a gunsmith check for head space and reset the barrel if needed. The guy running the die grinder on that job did a really good thing for you.
 
Wow. Your gunsmith definitely did not make that cut shown in the picture with a lathe and single point hardened steel tool. I would personally have a word with him. I think that you got burnt. the bolt may be salvageable by removing some material off the front of the bolt lugs and then refacing the bolt face again using a competent gunsmith, however there is some risk in removing this material that has been previously heat treated to meet Specifications. That outside layer of heat treated steel is what makes the whole rifle safe to function at the specified chamber pressure. I would be pissed especially on a well built BRNO. Sorry but that's my 2 bits
 
The Brno is not case hardened so removal of a little more metal won't compromise strength. However, there is no doubt that headspace will be affected. Have it properly machined and see where it ends up. Given the condition of that bolt, I would be surprised if the rest of the job is all that good either.
 
zthou said:
Wow. Your gunsmith definitely did not make that cut shown in the picture with a lathe and single point hardened steel tool. I would personally have a word with him. I think that you got burnt. the bolt may be salvageable by removing some material off the front of the bolt lugs and then refacing the bolt face again using a competent gunsmith, however there is some risk in removing this material that has been previously heat treated to meet Specifications. That outside layer of heat treated steel is what makes the whole rifle safe to function at the specified chamber pressure. I would be pissed especially on a well built BRNO. Sorry but that's my 2 bits
Click to expand...

I am curious...what would you gain by removing material from the front of the bolt lugs?
 
Can you post a picture of the cartridge setting on the bolt face. Is it setting high on the rough portion of the bolt? What does the fired brass look like? Was Brno rebarrelled? or rechambered? Might be repairable however needs the details I'm asking about.
 
The Brno was rebarreled with a stainless barrel. When the case is sitting on the bolt it appears to be sitting more on the tried side.


The fired brass have some groves in them the length of the brass and the base has some distortion I assume from the extractor and the force it took to pull out of chamber.



Also I checked for the bolt lug engagement with layout fluid and with light pressure from a cleaning rod against bolt face got the following result. Appears that only one lug is making contact.
 
I suggest you pull the barrel off and sell it for what ever you can get, strip the bolt apart, cut the bolt body in half and throw it away, sell the rest of the parts, action and stock for what ever... and walk away. In the end you will be farther ahead...
 
Jeez... that's a bit rough man... I honestly don't know if it is worth the time and money to get that gun into running order... depends how attached to it you are I suppose. Lot of stuff wrong with it.
 
You've got a tough decision to make. Guntech has given some solid advice and sometime it's better to sell off the parts and start over. However repair is an option if you know what needs to be done and can find a reliable person to perform the work. Your investigation tells me that the barrelling work was not done correctly. Both lugs need to make contact. If the bolt is original to the receiver and I'm assuming it is then there's the possibility of set back in the receiver. If the bolt is not original to the receiver I would go with a 98 bolt...pull the barrel, lap in the lugs and open up the bolt to suit your cartridge. If all good then turn your attention to the barrel. The marking on your brass indicates a rough chamber. Can it be polished out and maintain size? If not it needs to be set back and rechambered. Headspace would be set at this time. Talking a good size bill. yuor choice of what to do...no easy fix here! Ron
 
A 98 bolt is not the same as a ZKK bolt. From the looks of things, you have a messed up bolt face and a messed up chamber. It is probably repairable but at some cost. The gunsmith should stick to jobs he is capable of doing. He ruined a good rifle.
 
Did you check the lug engagement with the cocking piece removed. Mauser bolt race ways are fairly sloppy, and any upward pressure by the trigger sear assembly could lift the rear of the bolt and disengage the top locking lug.
 
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