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recessed crown under barrel threads?

 
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  #1  
Old 04-14-2014, 11:33 AM
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recessed crown under barrel threads?

so you here people saying that threading the end of the muzzel can cause the id of the barrel to open up a little because you are removing material. Well i was just thinking. Why not cut the threads and then crown the barrel with a recessed crown so that the crown is back behind the start of the threads in the barrel. Obviously it depends on how long you threads are as to how far you recess the crown.

Anyone tried it?
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  #2  
Old 04-14-2014, 12:24 PM
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Re: recessed crown under barrel threads?

I dont think it will be any better than any other crown. Ive threaded a few barrels and never seen accuracy or velocity loss after threading, as long as the correct thread is used.

My hunting rifle is a 30 cal chromoly barrel threaded 5/8-24 with an 11 deg crown and it shot exactly the same after threading the muzzle .75" back.
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  #3  
Old 04-14-2014, 07:19 PM
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Re: recessed crown under barrel threads?

On a regular Remington or Winchester sporter barrel the largest thread you can get on there and still have any shoulder is 1/2-28. On a .308 cal this leaves the barrel pretty thin. I haven't noticed the bushing or lead slug fitting loose enough to lose accuracy. I have frequently found that even with much thicker barrels, if the brake is put on too tight it will measurably constrict the barrel. Again accuracy rarely suffers from this effect.

Cutting a crown .600" deep before where a brakes baffles begin would make for a very weird installation. I like the end of the muzzle to end exactly where the port starts and taper back at 11 degrees to the crown.
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  #4  
Old 04-14-2014, 07:29 PM
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Re: recessed crown under barrel threads?

Quote:
Originally Posted by Hired Gun View Post
On a regular Remington or Winchester sporter barrel the largest thread you can get on there and still have any shoulder is 1/2-28. On a .308 cal this leaves the barrel pretty thin. I haven't noticed the bushing or lead slug fitting loose enough to lose accuracy. I have frequently found that even with much thicker barrels, if the brake is put on too tight it will measurably constrict the barrel. Again accuracy rarely suffers from this effect.

Cutting a crown .600" deep before where a brakes baffles begin would make for a very weird installation. I like the end of the muzzle to end exactly where the port starts and taper back at 11 degrees to the crown.
HG. by put o too tight do you meant he thread fit is tight or do you mean the brake is torqued on tight? how tight is too tight have you found? does this make it hard to then make for a "seamless" looking joint if the brake isnt tight?

It would be interesting if someone tried it. take a barrel with a break already on, measure the tenon length of the thread and then counter bore a crown slightly deeper than this.
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  #5  
Old 04-14-2014, 07:39 PM
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Re: recessed crown under barrel threads?

I meant torqued too tight. It can happed from around 15 foot pounds and up. On big threads it might take a hundred to constrict the bore. There is no set rule. It happens when it happens.

For a truly seamless fit it usually needs the joint sanded with the barrel. How tight it is has little to do with that. Don't be impressed by seamless fits when they are sanded. That is simple. Be impressed when a stainless brake is seamless up to a blued or coated barrel. That takes a sharp eye and a spot on dialing in on the outside of the barrel.
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  #6  
Old 04-15-2014, 08:57 AM
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Re: recessed crown under barrel threads?

Quote:
Originally Posted by Hired Gun View Post
On a regular Remington or Winchester sporter barrel the largest thread you can get on there and still have any shoulder is 1/2-28. On a .308 cal this leaves the barrel pretty thin. I haven't noticed the bushing or lead slug fitting loose enough to lose accuracy. I have frequently found that even with much thicker barrels, if the brake is put on too tight it will measurably constrict the barrel. Again accuracy rarely suffers from this effect.

Cutting a crown .600" deep before where a brakes baffles begin would make for a very weird installation. I like the end of the muzzle to end exactly where the port starts and taper back at 11 degrees to the crown.
+1
I have never seen any loss or gain in barrel/bore diameter doing it the same way as Hired Gun, so ether I have been lucky or just picked the right way to install a brake.

If you have a good class 1 thread fit I can see no down side.

Like many others I subscribe to the "KISS" method (Keep it simple stupid) and don,t over complicate
things and concern my self with the quality of work and components.

J E CUSTOM
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  #7  
Old 04-15-2014, 02:46 PM
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Re: recessed crown under barrel threads?

JE,
Have you ever really looked for the change in bore diameter? I found it by accident. I had a custom in from another smith with a brake on it for a barrel inspection. I cleaned it and visually inspected it and found nothing remarkable about the bore. I moved on to slugging it to check uniformity of the bore and found that it was really tight right in the brake threads. I loosened the brake and that cleared the constriction. That was how I discovered the bore constriction thing and then I went looking for it on every thread job. The best thread fit there is makes no difference. If the brake is torqued too tight it will constrict the bore. I can find it with bushings. Before you thread find the largest that will still go and when you are done with the brake job see if it will still fit. I found the small thin walled thread jobs were really susceptible to it. I originally just started not using so much torque but then had one come loose on a guy after a couple hundred rounds. So now rather than relying fully on torque I use blue Loctite on the thinner barrels.
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