Suppressors Threads off center

[QuiggyB]

I recently had a barrel threaded for a suppressor. Using a ball mic to measure the barrel seems to be .008 thicker at the 6 o'clock position than it is at the 12 o'clock causing me to think the thread job is .004 off center.

My question is - is this normal and within acceptable tolerances?

 

[762frmafr]

Re: Threads off center

Usually threads are cut to the bore centerline and not to the OD of the barrel. Who did the thread job?

 

[QuiggyB]

Re: Threads off center

I was attempting to measure relative to the bore centerline. I measured this by placing the ball of the ball mic in the bore and then measuring to the outside of the threads - same way I would measure case neck thickness. If it was perfectly centered I would have expected to get the same thickness all the way around.

The thread job was done by a local gun smith.

 

[762frmafr]

Re: Threads off center

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: QuiggyB</div><div class="ubbcode-body"> The thread job was done by a local gun smith. </div></div>

I would wager that it was centered off the OD of the barrel and not the bore centerline. Ask him how it was done. If it was not done to your liking ask that he re-do it to the bore centerline.

 

[QuiggyB]

Re: Threads off center

The main point of this question is to get some opinions on if it is still close enough to center to not be an issue or if there is the possibility of something like a baffle strike or something else happening. I assume getting it fixed would require shortening up the barrel and trying again which isn't desirable either.

 

[johngfoster]

Re: Threads off center

Rifling: groove vs land. Make sure you are measuring from the same relative point in a groove on each side or a land on each side. Otherwise it will be off by about 0.008", depending on caliber. This would be particularly important with a barrel like a 5R where there are not an even number of lands and grooves.

 

[762frmafr]

Re: Threads off center

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: QuiggyB</div><div class="ubbcode-body">The main point of this question is to get some opinions on if it is still close enough to center to not be an issue or if there is the possibility of something like a baffle strike or something else happening. I assume getting it fixed would require shortening up the barrel and trying again which isn't desirable either. </div></div>

Screw on the suppressor...pull the bolt and look down the barrel. If you see a complete round circle then you should be good to go. If you see a semi-circle, then more than likely you'll get a baffle strike.

 

[Cigarcop]

Re: Threads off center

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: QuiggyB</div><div class="ubbcode-body">The main point of this question is to get some opinions on if it is still close enough to center to not be an issue or if there is the possibility of something like a baffle strike or something else happening. I assume getting it fixed would require shortening up the barrel and trying again which isn't desirable either. </div></div>

"close enough" and suppressors shouldn't go together!

 

[762frmafr]

Re: Threads off center

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Cigarcop</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: QuiggyB</div><div class="ubbcode-body">The main point of this question is to get some opinions on if it is still close enough to center to not be an issue or if there is the possibility of something like a baffle strike or something else happening. I assume getting it fixed would require shortening up the barrel and trying again which isn't desirable either. </div></div>

"close enough" and suppressors shouldn't go together! </div></div>

Agreed....

 

[jonaddis84]

Re: Threads off center

I cant even imagine a way you could possibly measure accurately enough with how you are talking to say for sure whether it is good or not. Also if you do not have a very very high quality tube micrometer, those things flex like a mother, easily over .008".

The ONLY accurate way to tell is to chuck it up in a lathe, indicate the bore, and try to run a test indicator on the flat just before the shoulder.

 

[3DHUSKER]

Re: Threads off center

No way in #$%^ I let any of the local Smiths thread a barrel. I send mine to GAP. Cost more but I know it is right with no worries.

 

[flyrodder]

Re: Threads off center

I had a local 'smith thread a barrel, and he claimed it was concentric to the bore. When I had a baffle strike on THE FIRST BAFFLE it was apparent that wasn't the case. After 3 or 4 months of discussion and shipping and negotiation, YHM corrected the problem (cut and rethreaded the barrel, pressed in a new baffle stack, and refinished the can) and all I ended up paying for was the original threading, but what a mess.