Suppressors Question about threads

[JoshD]

I'm new to suppressors but have a Surefire on a form 3 going to my dealer. It will be used on 2 barrels, one being a 20" Lothar Walther and the other a Colt 14.5". I have not had the threads checked on either but I'm more concerned about the Colt barrel. I know ideally the threads should be as concentric to the bore as possible but is there a certain tolerance that is allowed or is a visual inspection sufficient? I need to make sure it will be right as the Colt barrel is brand new and I will have to pin/weld the muzzle device. It would be possible to mount the flash hider and install the can when it is released to me, and then do a visual before the pin/weld. It would just be easier to sell the barrel in stock form without a perm'd muzzle device if the threads are too far out.

I plan on having another barrel threaded in the future, so I could send the Colt barrel with it to have it checked. However, if it is 4 or 5 thou out, that really means nothing to me if there is no tolerance to hold. I cannot have it cut back and rethreaded because it would then be under 16". Making it a SBR is out of the question also, because I occasionally take it to a state that doesn't allow SBR's or silencers.

 

[thrusty]

Wait..... Could you repeat the question?

 

[JoshD]

When mounting a can, is there a max allowable tolerance the threads can be out of concentric to the bore? Can length is 6".

 

[thrusty]

When mounting a can, is there a max allowable tolerance the threads can be out of concentric to the bore? Can length is 6".

Way better!
Thunderbeast is the only reference I can point you to real quick. I don't know what would be considered the acceptable max allowable...but they do indicate their standard tolerance.
Thunder Beast Arms Corporation [TBAC] | Tech | THREAD SPECIFICATIONS

 

[ddavis]

When you get the can, mount it and look down the bore. You will be able to tell if it is on straight.

 

[thrusty]

^^^^ lol - unload the gun first.....

Not too many people can tell with their eyes if the axis is off by 0.002". Not until they have a baffle strike do they notice.
If you don't have tools to measure total runout of the threads...possibly a dowel that is nearest to the caliber down the can and into the barrel will give you a better guesstimate.

 

[SilentG21]

First off....your Colt barrel should be fine. Second, your Surefire adapter has to be installed with the supplied shims to be concentric. DO NOT use a crush washer for installation. If you are to pin and weld, Surefire makes pinnable brakes and flash hiders and I suggest using a competent smith to do the work. Surefire will also check that barrel for ya. Free if I'm not mistaken. Also check the Surefire vids on YouTube for correct installation of your hider/brake. Garin Lee at Surefire can help ya out with anything you need. [email protected] is his email address.

 

[Rancid Coolaid]

When you get the can, mount it and look down the bore. You will be able to tell if it is on straight.

I disagree.

And as the barrel gets shorter, I disagree more.

 

[ddavis]

I disagree.

And as the barrel gets shorter, I disagree more.

The human eye is more than capable of lining up two chunks of iron to make a projectile hit a target at hundreds of yards. How many thousandths off can you be to achieve this? I'd argue not much. Its not a perfect method but should give you a pretty good idea with obvious limitations, such as barrel length as you noted. It has worked for me so far and kept me from destroying my Cyclone on crappy AK threads. I threaded it on, and it looked obviously off center, so I got some threaded rod that I knew to be true and carefully fitted it to bore size. Sure enough, I would have had a baffle strike. To each his own.

 

[SilentG21]

I agree with ddavis. If something is wrong you should catch it or at least have a good idea. Just fyi.....your threads CAN be concentric and if you use the wrong mounting items such as a crush or peel washer your hider or brake will NOT be concentric.

 

[Rancid Coolaid]

I thought we were talking about precision, seems not.

Carry on.