I put in my paperwork and my check was cashed a couple of months ago, so my first 2 suppressors will be there just before the election (LOL).

I bought a QD 5.56 suppressor and a direct thread 7.62 suppressor.

I currently have a Sig 553P that has the -2 barrel which is 1/2x28 BUT replacement barrels are usually from demilled 552s and the barrels are threaded 14x1LH.

The only threaded adaptors that I can find are for the AK variants that convert 14x1LH to 5/8X24, which then means I could use my direct thread 7.62 can on my 553P if I did end up having to replace the barrel.

SO, what happens if you fire a 5.56 round THRU a thread adapter with a larger hole going into a 7.62 can?

Could you get a baffle strike?

I think the answer is yes, but minimal risk.

What about going thru a SECOND adapter, back from 5/8x24 back down to 1/2x28 shooting 5.56? Again, could you get a baffle strike?

I think the answer is yes, higher risk due to the longer time outside the barrel and it hinges on the ammo and the rifle twist stabilizing the projectile (i.e. 77gr out of a 1/9 or 1/10).

However, I'd rather ask the questions the "experiment" on my new suppressors when they get in.

James

Theoretically it should be doable, but the adaptors are just more points of potential failure. I say that not meaning that the adaptors themselves would fail, but the tolerance stacking could be an issue. Any little bit of play introduces the potential for something to be non-concentric to the bore.

Were it me I’d see about having the barrel re-threaded to 1/2x28 if that day ever came.

Spend a few bucks on a gauge. An alignment rod is a few bucks, but slip it in the bore and you will see if your stackup has enough concentricity to avoid striking the end cap or a baffle.

You know for sure, and it's a tool that pays for itself the first time you realize you didn't get things quite right on a new build and would have added a hole in the can.

I put an adaptor on a 6.5 Creedmoor Browning X-bolt, because they use a metric threading that isn't used on anything but some European auto brake systems. So I've checked the adaptor for alignment and the 30 caliber suppressor+adaptor for alignment. They both look good.

Coming from someone who has suppressed a couple of AK's using said adapters. If the barrel is concentric to began with, it's a none issue.

If your concerned about the effects of stacking multiple thread adapters, just have one made to your specifications. The cost will likely be more than two off the shelve adapters, but less expensive than a baffle strike.
I have bought custom made adapters from Mark McWillis at www.trosusa.com . He usually has the more common adapters in stock, but he can make just about any combination you might want. If what you want is not in stock I would order it now. The last custom one he made for me took about 3 months, but when it showed up it worked great. Good luck.

If the barrel length allows, cut the threads off, re-thread.

quote:

Originally posted by offgrid:
If the barrel length allows, cut the threads off, re-thread.

Agreed.

I have an adapter on my VZ58, and its been fine thus far but i do see it as a weak point in the system. If i was really going to go hard with the gun suppressed, i know id need to just get a VZ-specific suppressor since i cant cut the barrel and rethread.

quote:

Originally posted by RHINOWSO:

quote:

Originally posted by offgrid:
If the barrel length allows, cut the threads off, re-thread.

Agreed.

That's also what I'd do. Not only do you have to worry about tolerance stacking with multiple adapters, there is also a significantly increased probability of something coming loose at an inopportune time.

quote:

Originally posted by dfwglockguy:
If your concerned about the effects of stacking...
I have bought custom made adapters from Mark McWillis at www.trosusa.com .

Thanks. Obviously, I need 14x1 LH to 1/2x28 RH and I can't find it anywhere, so I'll probably just look up him and order a custom one, I have plenty of time.

quote:

Originally posted by offgrid:
If the barrel length allows, cut the threads off, re-thread.

Barrels on the 553 (and the 552) are like 8.9 inches, and there isn't a lot of room for rethreading. I thought of that idea too, but I don't think it's possible.

I need the 4 position gas valve anyway, plus there's time AND my 552 barrel hasn't been used much, but it would be good to have a backup. Not sure if I'll ever shoot enough to ruin the factory one, but I want to be prepared just in case.

Thanks all for the input!!!

James in Denver