Hello All:
I own a Sig Rattler in 556 and would like to put my favorite brake on it
The Sig Site does not have thread pitch published for the rattler
I didnt want to put a lot of torque on the device thats on it
Any info will be appreciated

Is the barrel already threaded? Measure the diameter with a caliper, micrometer or (easiest) bolt gauge and the thread pitch with a thread pitch gauge. Bolt diameter gauge Thread pitch gauge

I seem to recall reading this thread being 5/8-24 (5/8" diameter, 24 threads per inch), but don't hold me to it.

Capitol Armory has it listed as 1/2x28
https://www.capitolarmory.com/...ol-556-with-psb.html

However, I believe the OEM flash hider is pinned & welded.

If its pinned and welded then i cant get it off
or if i hit it with a torch, i might melt the weld but what about the pinning
will i ruin the barrel??

If it were mine, I would leave it alone. Muzzle brakes typically increase concussive blast. This would be even more dramatic with the Rattler's short barrel length. I suspect SIG pinned & welded the device to prevent installation of a suppressor because the increased pressure from such a short barrel would damage the suppressor.

Sig Cust service said the rattler is pinnned and welded in 556 not in 300
send me a instructional on how to remove the weld by using a end mill
i wanted to put a flash can that directs the blast even more forward but i will just forget that
Thanks for all the input guys !!

The 5.56 Rattler brake does not come off easily, it’s attached permanently to the gas block. A few gunsmiths have been able to remove them, but IMO, it’s not worth it unless you’re converting it to 22Lr only