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barrel diameters and muzzle brakes.

 
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  #43  
Old 05-20-2014, 10:59 AM
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Re: barrel diameters and muzzle brakes.

In an earlier post I stated I had repaired barrels that had shot the brake off for one reason or the other. (That is one of the reasons).

Just because "some" others have not had a problem doesn't mean I want to do it.

Muzzle brakes are a relatively new addition to rifles (I personally did not like or use them until
a few years ago when I realized the advantages they offered) Most rifles over 10 to 15 years old
do not have provisions for threading the barrels because they were not designed to attach anything to the muzzle, so barrel wall design thickness was based on finished barrel thickness.

A site sponsor that is one of the best gunsmiths, mentioned to me that he remembers while going to Gunsmith school he was told 'when drilling and taping site base holes in barrels never to go deeper than necessary and to leave .150 thousandths of barrel from the bore to the bottom of the drilled hole.

I looked in some of my gun Smithing books and they recommended the same thing.

I worry about the do it your self people that do not know there are minimums and could get into trouble. The gun smiths should take care of things like this (That's why you hire them).

As we are more and more into tactical firearms you will notice that none of the .308s have 1/2x28
threads (Most are 5/8x24) the , .223s still use the 1/2x28 because they can.

J E CUSTOM
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  #44  
Old 05-21-2014, 12:52 PM
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Re: barrel diameters and muzzle brakes.

Quote:
Originally Posted by stenger View Post
I have seen a lot of rifles use 1/2 inch brakes. Anyone ever have a confirmed problem with a. 308 cal brake with a 1/2 dim thread that the root cause was a thin wall!
I do a couple a week in 1/2-28. I use 9/16-24 when I can but many people do not like the look of the fat brake that goes with it. I would say hands down our most popular installation. Rem or Win sporters in 300 RUM. Followed by those skinny barreled Rugers in 7mm and 300 Win mag. It used to concern me but they have stood the test of time.
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  #45  
Old 05-27-2014, 08:09 PM
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Re: barrel diameters and muzzle brakes.

Quote:
Originally Posted by FEENIX View Post
This is another excellent info and should be on the "sticky".
Agreed!
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  #46  
Old 05-28-2014, 12:15 AM
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Re: barrel diameters and muzzle brakes.

Rhian,

It's been ages since my navy metallurgy training.

IIRC the term is nil ductility transition point. That beyond which plastic deformation occurs.

Just though I'm chime in. . .
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  #47  
Old 05-01-2015, 07:55 AM
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Re: barrel diameters and muzzle brakes.

So what is the minimum break wall thickness. I have a factory rem 30 cal barrel with a .644 muzzle. I bought a harrels break with a .750 od/9/16x32 thread. Will it be safe to contour this brake to the muzzle contour or close to it? I realize the walls are going to be really thin. Thanks
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  #48  
Old 05-01-2015, 08:16 AM
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Re: barrel diameters and muzzle brakes.

Quote:
Originally Posted by CHARLIEDUECE65 View Post
So what is the minimum break wall thickness. I have a factory rem 30 cal barrel with a .644 muzzle. I bought a harrels break with a .750 od/9/16x32 thread. Will it be safe to contour this brake to the muzzle contour or close to it? I realize the walls are going to be really thin. Thanks
Based on my conversations with barrel makers and engineers I made a simple guideline for tenon and thread size. it is based on .150 minimum barrel wall thickness between the minor diameter
of the threads and the rifle bore.

This minimum thickness is what the barrel makers use to flute a barrel, The thinnest number they gave me was .137 (depending on cartridge pressure and bullet diameter to) .150 thousandths.so
in order to error on the side of caution it did my calculations based on .150 thousandth wall.

A simple way to figure it is to take the bullet diameter, and add .300 thousandths. that will give you the Recommended barrel diameter for installing a thread for the brake. (Different thread pitches have different minor diameters but the .150 should cover it as long as you have enough barrel left over to have a shoulder to seat the brake against.

Hear is a link that may help.

www.jecustom.com - FAQ's

J E CUSTOM
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  #49  
Old 05-01-2015, 10:20 AM
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Re: barrel diameters and muzzle brakes.


Here is a pic of my father working on this gun patent:
Patent US3894471 - Rapid fire weapon for turret installation - Google Patents

I asked him how to calculate the max pressure in a gun [for my 45/70 handi rifle]
He showed me Lame's formula in a textbook for thick walled cylinders, that Lame figured out 500 yeas ago:
Stress for Thick Walled Cylinders using Lamé

Cylinder stress - Wikipedia, the free encyclopedia
Then he said that thin walled hoop stress was
Stress in the steel = [pressure][inside diameter]/[2][wall thickness]

I asked him where he got that.
He shouted in my face, "BY INSPECTION!"

I was late the the party, but I guess if someone has to tell you how to calculate thin wall hoop stress, you are stupid.
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