Muzzle threading diameter and accuracy

[Gil P.]

I came across an article from 2022 that showed the inside diameter of the muzzle on a few barrels threaded for 5/8-24 and 3/4-28. The 5/8-24 muzzles were slightly larger than the rest of the barrel, but only for the length of the threading.

This did not happen with the 3/4-28 threaded barrels.

Are the 5/8-24 barrels losing out on some accuracy potential?

Muzzle thread diameter article

 

[M-61]

Isn’t it 1/2-28?

 

[DaveTooley]

Depends on the manufacturing process of the barrel. Even then the target tells all and in my world no one complains about 5/8-24. To hedge your bet, larger is better.

 

[CJ6]

Question then..... What would the preferred thread/pitch/diameter be for a barrel diameter of 1.1-1.2" ?

 

[Chestnut]

To add to barrel thread discussion. Brownells did a video discussing over torquing a muzzle device (MD). As you torque an MD the bore gets constricted. This will have a larger impact than if the bore opens up imo.

The question to my mind is if the barrel is 0.6" shorter would that effect accuracy? If the answer there is no why would a loosening of the bore have any other difference? Is this all theoretical? It'd be interesting they they repeated the test with a properly torqued MD.

From first hand experience, i had my 270WSM hunting rifle threaded for a brake. Threads were 1/2-28. I saw an accuracy improvement because i stopped flinching when shooting the rifle. I never could get used to the recoil on that rifle.

 

[Old Navy]

All my heavy barrels are 3/4X28".

 

[CJ6]

All my heavy barrels are 3/4X28".

Diameter of barrel?

 

[Old Navy]

Diameter of barrel?

All are .984 +.

 

[Gil P.]

To add to barrel thread discussion. Brownells did a video discussing over torquing a muzzle device (MD). As you torque an MD the bore gets constricted. This will have a larger impact than if the bore opens up imo.

The question to my mind is if the barrel is 0.6" shorter would that effect accuracy? If the answer there is no why would a loosening of the bore have any other difference? Is this all theoretical? It'd be interesting they they repeated the test with a properly torqued MD.

From first hand experience, i had my 270WSM hunting rifle threaded for a brake. Threads were 1/2-28. I saw an accuracy improvement because i stopped flinching when shooting the rifle. I never could get used to the recoil on that rifle.

If you cut the barrel back, the bullet won't be touching the bore anymore vs if the bore is opened up at the muzzle, the bullet will still contact the bore, albeit a looser one.

 

[DaveTooley]

Question then..... What would the preferred thread/pitch/diameter be for a barrel diameter of 1.1-1.2" ?

What are you attaching to the barrel?

 

[LVLAaron]

I've noticed this on "less expensive" barrels. I can slide a pin in, until the shoulder.


FWIW: I use 3/4-24 - that seems to be a standard for big bore stuff. Don't know what uses 28tpi

 

[CJ6]

What are you attaching to the barrel?

Radial ported brake.
The 1.1" barrel will be in 6.5 cal.
The 1.2" barrel is 30 cal.

 

[Clancy]

I see no reason not to use 3/4 when you can.

 

[tommeboy]

It happens with button and cold hammer forged. And it does effects accuracy as gas comes out a lot more on barrels that are loosened up. That effects the base of the bullet and can steer it in a off center push on the base.

 

[TAJ45]

It seems l remember reading after Bill Calfee that the muzzle would open up a tenth or two.

 

[CJ6]

I see no reason not to use 3/4 when you can.

So what type of threads corse (24) or finer (32)?
I'm not planning on taking these off except for cleaning.

 

[2thdk]

There’s a good podcast where Erik Cortina interviews John Krieger. They discuss this very exact thing. Sounds like bores will open up on Button rifled barrels. No difference on cut rifled barrels, and cold hammer forged actually constrict and get tighter. IMHO, If your barrel contour allows it, go 3/4-24 regardless.

 

[CJ6]

They're both cut rifled Brux.

 

[marazzi59]

You could also back bore the barrel the length of the threads plus .100"

 

[dave@aDave]

It seems l remember reading after Bill Calfee that the muzzle would open up a tenth or two.

In Precision Shooting magazine, Bill also recommended to find the tight spot of the barrel bore and shorten the barrel to that length.
Some dispute that advise