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An interesting problem

907 Views 2 Replies 2 Participants Last post by  SigsRule
I have two Primary Weapons Systems combination brake and flash hiders. One was mounted on my XCR with no problem. The other was for my DSA FAL. The FAL is supposed to be 9/16x24tpi left hand thread and that's the PWS brake I ordered for it. I had difficulty taking the existing flash hider off the FAL so wound up taking it to my gunsmith to remove it and install the PWS. Turns out, the FAL threads aren't quite 9/16x24tpi. In fact it was off enough that the PWS wouldn't go on. The threads were about .032" too small. :mad:

Since I was planning to put a can on it eventually I decided to have the gunsmith rethread it 1/2x28tpi right hand - the barrel was too small in diameter to cut it 5/8". Checking with PWS, they said I could send the DNTC308 back and exchange it for a FSC30. The FSC is actually 5/8x24 but they also have 1/2x28 to 5/8x24 adaptors for $14.00.

The end goal is to get a SWR Omega .30 can and be able to swap it between the 5.56 XCR, the 7.62 XCR, The FAL, my 300 Weatherby, and my 7mm08 Encore with just a few adaptors for the ones not threaded 5/8x24tpi.

I had mentioned to Aussie Arms that the only other place I saw the 1/2x28 to 5/8x24 adaptor was asking $66.00 and he wondered if the tolerance on the PWS adaptor was accurate enough for the shoulder a can would need. Anybody know anything about this?
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Don't know if this answers your question, but I would avoid adapting an adapter. That is to say, I would use a max of 1 adapter. The more you use, the more your tolerance level goes up, and could lead to problems like not having the can concentric to the bore which = baffle strikes. A good machinist/smith can either thread or attach an adapter that will be concentric (with can mounted) to the bore. This would probably cost a bit more in money and time to have done, but if you are going to drop some dough on a can, it would be worthwhile to do this.

Generally, I have found that most decent factory barrels will take a standard can mount and keep it reasonably concentric, provided it is indexed evenly. Adding an adapter throws another factor into the equation. It can be done, but it should be checked with adapter - mount - and can attached. I would do this for each weapon that uses an adapter to fit the mount/can.

ETA: You could just use the ole' cleaning rod trick. It gives you a rough idea of concentricity. It is by no means a true check, but can alert you to possible alignment problems to have looked at.
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Everyone of the barrels that isn't 5/8x24 would only require one adaptor, but the concentricity issue is the concern with the $14.00 adaptor versus the $66.00 adaptor. FYI, the $66.00 adaptor is from a group that was mentioned by the folks at www.silencertalk.com. The PWS adaptor was obviously designed to fit their muzzlebrake/FH and it's concentricity may need to be checked for the tighter fit of a can.

The way it stands right now, the 7.62x39 conversion kit for the XCR was advertised as being 5/8x24. The 7mm08 will need to be threaded so it can be threaded for 5/8x24. I think the 5.56 XCR is supposed to be 1/2x28 and that's what I'm having the FAL threaded to, so the same type of adaptor would be needed for both. The 300 Weatherby is already threaded for a muzzle brake but I need to measure it to see what thread size it is.

I'm still waiting for my dealer to get the can in so we can start the Form 4 process so it'll be awhile before I have the can to check. In the meantime I'm going to need an adaptor for the PWS muzzlebrake/FH anyway and ordered the cheap one.
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