I had McGowen Precision Barrels make me a custom 16" .308 Winchester barrel for my Colt AR901. When I gave them the drawing specifications that I wanted on the barrel (contour, twist, finish, gas length, etc) I made a typo mistake and listed the muzzle threads as 5/8x28, when I meant 5/8x24, which is the standard AR10 muzzle thread pitch. I must have mistakenly mixed the "x28" part from the standard AR15 1/2x28 into the 5/8x24 when I wrote the specs. I got the barrel delivered 4.5 months later, today, and it looks great, with all my specifications, but I found out about my terrible mistake when I attempted to thread a 5/8x24 muzzle device.

Now I am trying to figure out what best to do to fix this problem. I am planning on running a SilencerCo Omega on their ASR muzzle brake. SilencerCo makes an ASR 7.62 muzzle brake in 1/2x28 thread. Could I safely have the threads redone to 1/2x28 on the barrel and still run the Omega suppressor with that mount out of a .308 Winchester barrel? Are there any safety issues with going 1/2x28 threads on a .308 Win rifle? Obviously I would have to make sure I dont ever use a 5.56 muzzle device on it.

Cutting the barrel and rethreading is a no-no, as the barrel is already 16" and I have a lightweight contour on the barrel so I dont think there would be much material diameter if we cut.

Thanks for the help.

I found out SilencerCo also makes an ASR muzzle brake with 9/16x24 RH for the Omega.

Would this thread be better suited and can it be turned down from the incorrect 5/8x28 threads?

Thanks

Contact Morgan (eastTXhunter) he should be able to sort you out, here's his EE thread Barrel Threading sale $50, PTR 91, Tavors, Augs, Scar, Sig MPX, Beretta 21A Threading, FAL, PAPM92

Thanks for the reply. I'll keep this in mind. I have used ADCO in the past for other barrel mods, so I have been in contact with them. They said they can turn down from 5/8 to 9/16 no problem. So I think that's the way I may end up going with. They also said they can "replace" the threads with a different service. I am not sure how this "replacement" works, but I think it has something to do with making a custom adapter or sorts that sits flush with the barrel. I asked for more details on this service from them. But I am not sure I want to add any more variables to the barrel harmonics equation by having an "adapter".

I may just get it turned down to 9/16x24 RH since the Omega has a mount in that thread.

nvm

Just cut the threads off and have it re-threaded.

It will be shorter.

Can't. As stated in the OP.

Buy a 1/2x28 muzzle break and have it drilled and tapped to 5/8x28. There should be plenty of meat to do this.

What's your barrel diameter behind the muzzle?

I would cut and pin the new device and not jack around with oddball muzzle wall thickness and reaming 1/2x28 devices.

Seconded. Dependant on barrel thickness, cut and pin it. Pretty sure whatever Adco suggests, just do.

Barrel diameter behind muzzle is .600", not counting the muzzle shoulder. Threading on to what is currently the muzzle shoulder would not work either as I need a shoulder to brace the muzzle device against (shims, crush washer, etc).

Both ADCO and McGowen have responded and suggest to either turn the threads down to 9/16x24 RH and use the SilencerCo muzzle device threaded for that, or ADCO also optioned to have the threads "fixed" by using their thread fixing service which essentially threads the muzzle down and installs a custom "adapter" pinned and flush with the barrel that has the correct external threads 5/8x24.

So far McGowen has offered to thread down to 9/16x24 RH at no cost and out as quickly as they can. So that is what I am going with for now. If in the future I need to return to 5/8x24 , then I'll have to get with ADCO. I dont plan on running anything other than the Omega on this rifle.

Yep, go the McGowan route.