I just got a new muzzle brake for my AR the other day.  It's a Diamondhead T-Brake.  What was on it was a flash suppressor (the rifle itself is a Radical).  So I unscrewed it and screwed on the new one.  It's supposed to be mounted a specific way... it's kind of triangular in appearance, with the "point" facing upward.  The only way I could get that to happen was to stack the crush washer from the old flash suppressor and the one that came with the T-Brake, and then it was 1/8 of a turn with a wrench.

So, the questions... first, is this okay?  If not, what do you suggest?  I didn't want to have to crank down on it too hard and risk stripping the threads on the barrel.

Thanks.

Rob

Use only the new crush washer that came with the new muzzle device.

After you achieve "hand tight", you should be able to get another full rotation on it while the crush washer "crushes".  Don't worry, you wont strip the threads, there will be some resistance at first then it will have a consistent torque while you rotate it into position.

Try not to overshoot the timing, as once crush washers are crushed, they don't spring back, so you'd have to get a new one and start over.

Stacking the crush washers is a bad idea...and once they're crushed to final position, you're not supposed to re-use them.  You should take it off and start over with a single washer.  

Crush washers have enough give in them that they will crush 360 degrees + after first contact, so you shouldn't worry that you're gonna bung up the threads.  
They can be a little tough starting out, but then they'll just keep on going.  
Is your crush washer facing the correct direction.  Think of it like the bell on a trumpet, the concave side faces forward.  
As long as you crush it through a minimum of 90 degrees rotation (1/4 turn), then you are good to go.

Awesome, thank you!  I'll take care of that tonight before I head to the range in the morning.

You will not screw up the threads on your barrel.  Crushing a new crush washer is going to take a bit of torque too.

The other thing is to make sure you're supporting the barrel/upper in the correct way when installing/tightening the muzzle device.  You'll need a bench vise plus barrel blocks, a reaction rod, or a BEV block.

I have a Rock River R3 upper and I want to change the factory muzzle brake but RRA advises against as it will take away the accuracy. has anyone change one on an R3 and had any problems and did it help.

I can't really see how accuracy would be permanently effected but putting on a new MD can and usually does shift POI. I always go to barrel blocks with a vice manually. It's cheap and no risk of any damage.

Thanks, anything on why Rock does not want you to change there brake? Has anyone changed there brake to an aftermarket one and anything happened or is it just a gimmick?

Crush washers are rated for 1-1/4 turns.
Minimum 1/4 turn then rotate to final position.

They dont want you to change it because its not factory and thus they can't help with any accuracy issues you may have with an aftermarket device.  The standard manufacturer response will always be "dont touch it.  Let our guys do it for you."