AAC Muzzle Brake Installation Question

Omega_556 · **Posted:** Thu Apr 09, 2009 11:09 pm

I just received my M4-2000 1/2-28 TPI brake, nice piece, I can't wait to shoot it.

I was reading the instructions, yeah I actually read them, and the excerpt below made me curious.

AAC Instructions wrote:

... the ports of the muzzle brake must be oriented at 9 and 3 o-clock. The ideal method of achieving this orientation is to have a depot level armorer machine a stainless steel washer of the proper length that allows the muzzle brake to thread on so that the ports align at 9 and 3 o-clock. ..."

I have a lathe and some machining experience, but how in the hell do you machine a stainless washer that is say 0.035"?

It took 28 lb-ft of torque to perfectly align my brake with a 0.010in shim. Clearly I don't need to turn a custom shim, but I'm curious how it would be done.

Outsydlooknin75 · **Joined:** Tue Apr 07, 2009 2:58 pm **Posts:** 106

Im thinking PEEL washer .... or .15 or larger shim

1_ar_newbie · **Posted:** Fri Apr 10, 2009 7:56 pm

Glad your brake went on with out a problem!

I will ask the guy that wrote the instruction about that other bit...

AAA · **Joined:** Sat Jul 09, 2005 7:17 pm **Posts:** 714

The way we do it is to simply drill a hole in a piece of barstock and part it off.
It generally takes a pretty ridgid machine to part off and leave a smooth surface finish.

If it needs to be trimmed to size we use whats call emergency collets. This picture pretty well says it all.

Omega_556 · **Posted:** Fri Apr 10, 2009 8:36 pm

Great illustration, how thin of a washer can you make with this method?

Outsydlooknin75 · **Joined:** Tue Apr 07, 2009 2:58 pm **Posts:** 106

So basically the collet is an expendable part and a one time use?

AAA · **Joined:** Sat Jul 09, 2005 7:17 pm **Posts:** 714

The collets locks into a collet chuck which squeezes it, so you'd need to have a 5C collet chuck on your machine. The collets are soft material and can easily be machined for another job. %c Emergency collets are a easy to acquire at auction used.
As far as how small a piece of material, dunno, the smallest I've personally ever held is probably only 0.020 or so. I'm sure you could go smaller than that, but you'd eventually reach a point where the collet would crush the material, that's where you have to switch to a surface or Blanchard grinder.

FYI I didn't do the illustration, it's just off the web.

Omega_556 · **Posted:** Sat Apr 11, 2009 4:33 pm

I got my equipment at an auction, and I have a collet chuck, I've just never used it. I guess it's time to get an emergency collet.

Also, thanks for the lead to www.home-machine-shop.com, interesting site.

Braidon · **Posted:** Sat Apr 11, 2009 6:57 pm

I would say a grinder is the best method for this, we have ground some shims on our surface grinder that were .0004", it was a obscure shape and needed ports through the shim so we made the part at .100" thick on a 5 axis and then put it on the grinder and took it down the the .0004" I personally didn't work on it but I know that guy who did it only felt comfortable drilling the ports with a piece of material that was at least a .100". So what I would do would be make over size washer with the correct OD and ID then grind it down to fit.

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AAC Muzzle Brake Installation Question

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