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New barrel from manufacturer chambering

Bill58

Plastic
Joined
Nov 12, 2023
I am going to purchase a new barrel from recommended manufacturer. When buying a new barrel 338 caliber. Is the neck already cut into the chamber? I don't know what needs to be done to specifically the chamber.
I understand that the boar and muzzle have to be threaded to install. My interstate is what needs to be done to get the chamber neck cut. I am not sure which neck will work best a .365 OR .368 neck? I want to shoot 200 gr - 300 gr bullets. Any help would be appreciated. Thanks, Bill
 
While chambering a new barrel is not "rocket science," it is not something that should be tried without experience or a hands-on mentor. Internet coaching is not the way to do this. If you do not know how to operate a lathe, this will be beyond your skill set.

To answer your questions:
Is the neck already cut into the chamber? Probably not unless the barrel is short-chambered which is not likely in a .338. It would be cut along with the rest of the chamber with a chambering reamer.

I am not sure which neck will work best a .365 OR .368 neck? You don't say which .338 cartridge you are interested in; I am assuming .338 Win Mag. I would not worry about the neck diameter as the reamer will have one appropriate for the cartridge. Tight necks are for match rifles, not hunting rifles.

I understand that the boar and muzzle have to be threaded to install. This is not correct. The chamber end of the barrel needs to be threaded to fit into the receiver. The muzzle end only needs to be threaded if you intend to put on a muzzle brake or something similar.

You will be far and away best served by finding a good gunsmith and having him do the work. Trying it yourself is risking destroying the new barrel or worse.
 
I had a nonstandard reamer (rimmed cartridge) made and sent it to the barrel manufacturer. They cut off the chambered end to length and reamed it for me. I threaded it and cut off the muzzle end and finished it. Worked well for me as I did not want to build a flushing rig to ream only one barrel. Had I been doing a rimless cartridge barrel I might have had them short chamber it so I could finish it by hand. I have threaded many barrels so that part was a piece of cake.

Edit.
Pac-Nor is the barrel company that I used. Others would probably do the same.
 
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I have most of the hardware for a flushing system. Made an internal center from hollow ground shaft for short barrels. Current thinking is not to bother. Yet another 'coolant' tank to maintain, and I want to inspect the reamer every step of the way. And I'd rather be using real cutting oil as well.

I've seen a couple of barrels done by 'pro's' that aren't as smooth in the throat as they could be. And they copper foul like crazy until that wears itself smooth. I generally get no copper in mine ... to 'mine' ;-)
 
Follow up, a pre'chambered barrel will be chambered a bit deep. It's your job to set the shoulder for proper headspace.

Gauges are recommended ... new brass and a couple thou' extra is 'passible' ...

Note, belted mags are gauged off the c'bore for the belt, not the base to shoulder dimension. Which means, like it or not, you have to trust whoever ground the reamer ...

I've seen a couple of WTF's ...
 
A word of caution to the untrained as others have said. Shooter on my range screwed a chambered barrel into a Tubb. Head spaced correctly although he never checked this. Fired a few shots all difficult to chamber. Case ruptured and blew out the extractor, cracked all four corners of the mag well in the lower, blew out the bolt release and dislodged the cross pin holding in the firing pin. Wore a piece of the ruptured case in the head and would have got one in the eye if he hadn't been wearing glasses. Turns out the barrel cone was too deep and the case was unsupported. Additionally the Tubb has no exhaust gas port for a case rupture. The only way this would have been picked up was either using a case or head space gauge to check the length of unsupported case prior to screwing in the barrel. Get someone who knows what they are doing to check everything before installing the barrel and if you insist on doing your own work with no training or prior experience then fire the rifle from a cradle with remote activation. A poor mans cradle used to be improvised by tying the rifle to a tire and pulling the trigger with a length of string.
 
A reputable barrel manufacturer will help spec a barrel (twist and profile) and any decent reamer maker will be able to supply a reamer to standard or custom spec if needed.

A blank won't have a neck. Your reamer will cut the neck as well as the rest of the chamber. The neck diameter needs to be discussed with your reamer supplier.
 
A word of caution to the untrained as others have said. Shooter on my range screwed a chambered barrel into a Tubb. Head spaced correctly although he never checked this. Fired a few shots all difficult to chamber. Case ruptured and blew out the extractor, cracked all four corners of the mag well in the lower, blew out the bolt release and dislodged the cross pin holding in the firing pin. Wore a piece of the ruptured case in the head and would have got one in the eye if he hadn't been wearing glasses. Turns out the barrel cone was too deep and the case was unsupported. Additionally the Tubb has no exhaust gas port for a case rupture. The only way this would have been picked up was either using a case or head space gauge to check the length of unsupported case prior to screwing in the barrel. Get someone who knows what they are doing to check everything before installing the barrel and if you insist on doing your own work with no training or prior experience then fire the rifle from a cradle with remote activation. A poor mans cradle used to be improvised by tying the rifle to a tire and pulling the trigger with a length of string.
A case or a head space gauge wouldn't have shown a bolt nose clearance problem.

Possibly some soft lead wire or plastigauge would have been the simplest method without getting into making a custom gauge with depth mic setup
 
I dont see how you could get that kind of clearance anywhere in a gun ,unless you actually did it on purpose ......'Kentucky Ballistics ' Blowup of the week utube.
 
A case or a head space gauge wouldn't have shown a bolt nose clearance problem.

Possibly some soft lead wire or plastigauge would have been the simplest method without getting into making a custom gauge with depth mic setup
Incorrect. You know how far the case needs to protrude and you know the distance from the bolt to the front of the action from there it's simple math and a depth micrometer to arrive at the value. Anyone who can't do this shouldn't be chambering or fitting barrels.
 
I dont see how you could get that kind of clearance anywhere in a gun ,unless you actually did it on purpose ......'Kentucky Ballistics ' Blowup of the week utube.
My thought is someone couldn't get the gun to feed and put a deeper countersink or potentially changed the angle. There was significant chatter in the cone which makes me think it wasn't the original single point cut cone. Currently in the running for the Darwin award.
 
Case ruptured and blew out the extractor, cracked all four corners of the mag well in the lower, blew out the bolt release and dislodged the cross pin holding in the firing pin. Wore a piece of the ruptured case in the head and would have got one in the eye if he hadn't been wearing glasses.

And that's why I shoot 22LR rifles (not the only reason but....)
 
Coned breeches, I draw them up in CAD and determine a better, shallower, angle that clears the bolt and adds support at the head of the case. Never noticed any change in feeding.
Problem is you know what you are doing unfortunately a lot don't.
 
Incorrect. You know how far the case needs to protrude and you know the distance from the bolt to the front of the action from there it's simple math and a depth micrometer to arrive at the value. Anyone who can't do this shouldn't be chambering or fitting barrels.
Ok school me. Show me how to measure the position of the cone with a depth mic and a head space gauge on a kelbly. The cone is a continuous taper to the chamber so there is nowhere for the depth mic to reference.

Normally use a ball or a tapered plug in conjunction with a depth mic and a collar.
 
Normally use a ball or a tapered plug in conjunction with a depth mic and a collar.
there we go. Collar or sleeve over the tenon to give a reference plane and a ball to sit on the angle.

We were talking about a prefit that's easier.
  • Drop case or preferably head space gauge in chamber before fitting barrel.
  • Insufficient case support will be visible.
  • Fit barrel.
  • Insert and close bolt. Bolt doesn't close cone is not deep enough.
  • Check head space.
  • As the head space in this case is off the shoulder you know if the bolt closed and the head space is correct there isn't a problem.
 
Trigonometry is your friend. You can always cheat and let CAD do the trig.

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