Best way to check for concentric threading

freeborn60 · Post by **freeborn60** » Tue Jun 02, 2009 11:02 am

I recently got my first sound suppressor (.30 cal and QD if that makes a difference) and have some barrels that are already threaded. What is the most effective way to make sure the threading is concenctric to the bore? I've heard everything from just looking through when the suppressor is mounted, shining a light through, using a laser boresighter, etc... which is the best?

Thanks!

smcharchan · Post by **smcharchan** » Tue Jun 02, 2009 11:29 am

Long, heavy bullet fired at subsonic speeds. You'll know then.

Just kidding. Welcome. I don't know how calibrated your eye is, but I would recommend taking it to a gunsmith to have it checked out.

I'm sure that some folks here will provide some other ideas.

David Hineline · Post by **David Hineline** » Tue Jun 02, 2009 8:46 pm

The best would be to send every rifle you are going to mount the silencer on to the original manuf. of the silencer to get verified in writing that that the alignment and mounting is proper. That way when things to sideways the silencer manuf. can not blame it on the rifle.

Omega_556 · Post by **Omega_556** » Tue Jun 02, 2009 9:05 pm

David Hineline wrote:The best would be to send every rifle you are going to mount the silencer on to the original manuf. of the silencer to get verified in writing that that the alignment and mounting is proper. That way when things to sideways the silencer manuf. can not blame it on the rifle.

Do I sense a heavy dose of sarcasm, or are you serious?

What is AAC going to do when I contact them to send in 8 AR upper receivers? What kind of turn around would that be?

freeborn60 · Post by **freeborn60** » Wed Jun 03, 2009 9:31 am

Well, I guess technically David Hineline's response would be the *best* option...and that is what I asked for, but I should have been more clear.

Is there anything I can do by myself, such as with a object/tool I could buy?

CKOD · Post by **CKOD** » Wed Jun 03, 2009 10:00 am

Mc Master Carr part number 88695K25 Its a 36" long precision ground drill rod blank, .302 +/-.0005 in diameter.

Very carefully slide this down the bore of the silencer/barrel. It is tool steel, so you dont wanna go smacking your crown, etc... Slide it down the barrel and it should fit easily without binding or rubbing on the suppressor at all. Especially since its .005 undersized.

Other methods may work, but for $4.50 + shipping I'd say its cheap confidence.

J Krammes · Post by **J Krammes** » Wed Jun 03, 2009 12:32 pm

Could you just use calipers?

Jeremy

David Hineline · Post by **David Hineline** » Wed Jun 03, 2009 1:00 pm

For the at home user, if your eye is trained that works very well, or one of the laser bore sighting cartridges cover the exit of silencer with masking tape and see if laser hit the center of the exit hole.

Fudmottin · Post by **Fudmottin** » Thu Jun 04, 2009 3:45 am

Another way to go is to just run a cleaning rod through the breach end and see that it comes out the end cap without touching anything in the can.

Or you could turn down a piece of aluminum bar to the land diameter and push that through in the same way. Then see how much clearance there is. It should be more than the height of the lands to the grooves.

Do pre-threaded barrels often have problems with concentricity?