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BAT Bolt Cone face machining

SG4247

Hey all,

I have a BAT 2 lug coned face .308 style bolt. It is too close to the mating cone face on the chamber entrance.

It needs about .010" removed from the 25 degree cone face.

Is this something a competent machinist/smith can do? Or does it need to go back to BAT?

Seems like the bolt handle is in the way of chucking it up.
 
SG4247 said:
Hey all,

I have a BAT 2 lug coned face .308 style bolt. It is too close to the mating cone face on the chamber entrance.

It needs about .010" removed from the 25 degree cone face.

Is this something a competent machinist/smith can do? Or does it need to go back to BAT?

Seems like the bolt handle is in the way of chucking it up.
Click to expand...
The material needs to be removed from the barrel, not the bolt. Any gunsmith/machinist thats DDTC registed should be able to do it.
 
Got a number for a guy with ITAR and EAR registration? Prolly not...

But.. I have two bolts. One barely goes into battery and and sometimes wont during a match if there is any carbon or debris at all. There are scratches on the cone face. The other (spare bolt) hits the barrel face before the lugs even engage. So the bolts are slightly different.

I want to face off both bolts. One by a little say .004" (one im shooting) and enough off the spare (.010" at least) so it can be used in case of an emergency.

Barrel machining is my last choice.
 
I'm sure you have your line of thought on this
But IMO barrel machining should be your first choice
Since it is not. I wouldn't trust them to anyone other than Bat.
 
Well, I suppose I could cut the barrel tenon - so that the tight bolt meets the spec of .004"-.010" and allow the other bolt to have more.

Is the clearance specified by BAT for shooter safety in the event of a case rupture?
 
Have you double, triple checked the tenon to make sure it is to Bat spec?

I have seen people cut the wrong angle on the barrel for the cone bolt
Are you doing this barrel work yourself?
 
Tim Singleton said:
Have you double, triple checked the tenon to make sure it is to Bat spec?

I have seen people cut the wrong angle on the barrel for the cone bolt
Are you doing this barrel work yourself?
Click to expand...
^^^^^^^^^^^^^^^^^^
What Tim said.
I am sure Bat will recommend the tenon cut.
Please let us know what you decide.
 
SG4247 said:
Got a number for a guy with ITAR and EAR registration? Prolly not...
Click to expand...
Funny thing is,, I do! But they're probably not interested in working for someone who thinks they'll tell 'um how to do it! "All ya' gotta' do is......." If you want the bolts "matched", consult Bat. After they are "matched" (depending on what Bat says/does) the tenon will need to be adjusted.
 
Last edited:
SG4247 said:
Hey all,

I have a BAT 2 lug coned face .308 style bolt. It is too close to the mating cone face on the chamber entrance.

It needs about .010" removed from the 25 degree cone face.

Is this something a competent machinist/smith can do? Or does it need to go back to BAT?

Seems like the bolt handle is in the way of chucking it up.
Click to expand...


CALL BAT........... THEY`LL FIX IT RITE...........
bill
 
There isn't anything wrong with the bolt if it came from BAT machine and hasn't been molested buy Bubba the gun plumber...

Cone breeches can be tricky and if you have the angle of the breech in the barrel wrong - you will become a dog chasing his tail. Did the smith measure the angle of the bolt and did they set the machine to the correct angle when they breeched the barrel? The correct fix is to remove the barrel and investigate the angle of the breech on the barrel. It sounds like the breech angle was NOT cut correctly. If you just start removing metal without examining WHY it's rubbing you will go down a VERY dark path.

There are plenty of high quality smiths on the fourm that can help with this, but I would pull the barrel and confirm the angle of the breech matches the angle of the bolt. You won't know what to do until we figure out the angle of the barrels cone. Even 1-2 degrees off can create the problem you have.

Good luck and keep us posted!!!

Barrel Brothers
 
I agree with the op, in that, there has to be a difference in the bolts, if one closes with a given barrel but the other doesn't, with the same barrel.
 
Umm - I failed to see there are two bolts... after re-reading - with more coffee in me - I would measure both bolts for the angle on each bolt. If both bolts have a negative breech (which it sounds like) then the breech on the barrel will need to be adjusted either way. Confirm that the barrel breech angle is off. It might be a quick fix just by recutting the breech - recheck headspace if you change the angle of the breech.

If you want (2) bolts match one bolt to the exactly to the other - recheck they are the EXACT same angles and the exact same dimensions. I bet you will currently have 3 different angle measurements - (2) bolts and the barrel will all be different angles.

One bolt is a BAT machine - is the other a BAT bolt as well?

Barrel Brothers
 
Last edited:
BarrelBrothers said:
Umm - I failed to see there are two bolts... after re-reading - with more coffee in me - I would measure both bolts for the angle on each bolt. If both bolts have a negative breech (which it sounds like) then the breech on the barrel will need to be adjusted either way. Confirm that the barrel breech angle is off. It might be a quick fix just by recutting the breech - recheck headspace if you change the angle of the breech.

If you want (2) bolts match one bolt to the exactly to the other - recheck they are the EXACT same angles and the exact same dimensions. I bet you will currently have 3 different angle measurements - (2) bolts and the barrel will all be different angles.

One bolt is a BAT machine - is the other a BAT bolt as well?

Barrel Brothers
Click to expand...
Huh???o_O
 
If both bolts won't close or rubs on closing - the breech on the barrel is cut at the wrong angle or needs to be cut deeper. The smith should measure both bolt's angle - are they the same? Then measure the angle of breech in the barrel.

Since we have rub on one bolt (scratches on the bolt) and one won't close at all - the breech in the barrel is negative - not cut correctly. Even if he machines one bolt to match the other - the barrel breech is still off and will need to be adjusted. There should be a gap of at least .002" between the bolts cone and the barrels breech. Since he is rubbing on the one that closes - the barrels breech is not correct.

Barrel Brothers
 
Scratches don't tell us much. Depending upon how much clearance it was set up to have, without a cartridge or gauge in the chamber, the bolt nose may well contact the barrel breech when opening...even with proper and matching cone angles on the barrel and the bolt nose. The firing pin spring will hold the bolt rearward while cocked. So, it could have come in contact, or have been cycled with debris between the bolt nose and the end of the barrel tenon, and caused the scratches. That just doesn't tell us definitively that the cone angle on either is right or wrong. Depending on clearance, with an empty chamber, either the bolt handle OR the barrel and bolt nose contacting one another, is what stops the bolt's forward movement. Either way, if one closes and the other doesn't, there IS a difference between the two bolts.
 
Thanks for the input guys.

Not to complicate this further...

I have two BAT bolts, one I am currently shooting in F-open using a 6x47 Bartlien which barely fits. If the chamber entrance gets very dirty, this bolt wont close. My second spare BAT bolt doesnt come close to closing on an empty chamber.

I also have a second brand new krieger barrel in 6.5x47 headspaced to the same action and supposedly cone face cut to match the bolt currently in service.

I guess im going to send all this mess to someone to who can straighten it out - after the end of the season.

Any suggestions as to who can fix it - is appreciated.
 
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