Does barrel thread pitch matter ?

[Timo Turl]

Does the choice of barrel thread pitch matter when it comes to consistent accuracy in a competition rifle ?

With the move to heavier barrels, is the weakest link now in the crown if you choose a thread pitch that takes off more “meat” than one that doesn’t ?

Assuming all work being equal, should we favour thread pitches that leave as much metal around the crown as possible, as that’s likely to be the first part of the rifle to go from an accuracy perspective under heat / long strings of fire ?

Is one thread pitch more suitable for competition than another ?

Thanks, curious to hear your thoughts.

 

[jcmullis2]

In a word, yes.

 

[308pirate]

Are you talking about breech threads or muzzle threads?

 

[308pirate]

In a word, yes.

I'd love to hear an explanation based on data

 

[308pirate]

Does the choice of barrel thread pitch matter when it comes to consistent accuracy in a competition rifle ?

With the move to heavier barrels, is the weakest link now in the crown if you choose a thread pitch that takes off more “meat” than one that doesn’t ?

Assuming all work being equal, should we favour thread pitches that leave as much metal around the crown as possible, as that’s likely to be the first part of the rifle to go from an accuracy perspective under heat / long strings of fire ?

Is one thread pitch more suitable for competition than another ?

Thanks, curious to hear your thoughts.

Pitch has nothing to do with how deep threads are cut or how much stock is removed from the barrel. Major and minor diameter do.

If you're going to try to have a technical discussion at least know what you're talking about.

 

[DAVETOOLEY]

On premium quality, after market barrels history says it doesn't matter. Common sense says in the long run bigger will win out.
I often wonder why people send me brakes with 5/8-24 TPI threads for a barrel that's .900"+ in diameter.

 

[Timo Turl]

On premium quality, after market barrels history says it doesn't matter. Common sense says in the long run bigger will win out.
I often wonder why people send me brakes with 5/8-24 TPI threads for a barrel that's .900"+ in diameter.

What would you suggest instead?

 

[DAVETOOLEY]

What would you suggest instead?

Just move up to 3/4"

 

[SharpsNitro]

Pitch has nothing to do with how deep threads are cut or how much stock is removed from the barrel. Major and minor diameter do.

If you're going to try to have a technical discussion at least know what you're talking about.

Editing my original response to make it cleaner and more precise. Your statement is incorrect. For the 60 degree thread profile all you need to determine the material removed is one dimension of the thread (one leg of the triangle) so both the thread depth or the thread pitch will work.

 

[Baron23]

metal around the crown as possible, as that’s likely to be the first part of the rifle to go from an accuracy perspective under heat / long strings of fire ?

Really, and I thought it would be chamber throat erosion????

 

[want2learn]

without confusing the issue
....are screw in barrels best integrated into the receiver by virtue of a screw in mechanism as opposed to one in which the barrel extension slides into the receiver and is clamped in place like the Sig SSG3000?

or rather what is the best way (accuracy and precision) of integrating a barrel to the receiver assuming they're 2 individual pieces?

 

[308pirate]

Editing my original response to make it cleaner and more precise. Your statement is incorrect. For the 60 degree thread profile all you need to determine the material removed is one dimension of the thread (one leg of the triangle) so both the thread depth or the thread pitch will work.

You don't need to do any math if you're cutting threads to a standard, like ANSI/ASME B1.1. Everything is spelled out there for you.

And your approach ignores the thread root.

 

[SharpsNitro]

Reread your original assertion that thread pitch has nothing to do with how deep a thread is cut or how much stock is removed from a barrel because it is completely wrong and bringing up B1.1 and thread roots doesn’t change that (the root is 1/4 of the pitch). Go back and look at the basic profile of the Unified Thread Standard, it is all driven off of pitch (you could say height also but that is derived out of pitch and basic trigonometry so it’s not really independent).

 

[dimar1492]

I like 3/4-24 on Heavy Palmas or really anything .875" or bigger at the muzzle.

 

[Wheres-Waldo]

If we are having this discussion, perhaps we should involve the torque specifications of muzzle devices...

1/2-28 threads with nothing torqued on them do nothing beyond any deformities introduced during machining. A muzzle device that’s self timing with 15 in-lbs of torque likely does little as well. A flash hider and crush washer at 80 in-lbs... maybe more... who knows

 

[SN13]

Well one reason I run 5/8x24 is that my suppressors fit that thread.

 

[1moaoff]

Dumpster fire about to start?

 

[samb300]

@TJC I have over-analyzed this for the past couple years, and couldn't figure out why I'd want to take a barrel that is 0.930" dia at the muzzle and machine it down to an undercut diameter of 0.575". I have been using M18x1 threads for extra material (0.653" dia undercut), but plan to go to 3/4-24" as Dave suggested above for even more material to remain.

One caveat is you'll have to select threads that work with your chosen muzzle device(s). I use factory TBAC brakes for their suppressors, which are offered in all the sizes. For the majority of off the shelf self-timing brakes, they're all 5/8-24".

A second caveat is all the research I've done shows that for premium cut-rifled barrels, the muzzle thread diameter doesn't really matter. It's only with button barrels or other forms of rifling that may release residual stresses when machined that the muzzle might "bell" open.

One last thing to consider is that lots and lots of guys on the PRS circuit do just fine with 5/8-24" threads, so there doesn't appear to be a statistical significance to that thread size causing any issues downrange. Hell, I always do a double take when I see a TacOps rifle in 308 with a measly 9/16-24 muzzle thread haha, and from what I can tell those all shoot