Got a MB556AR to mount to a 12.5" upper and it's a pain in the ass to
get the suppressor index pin notch bottom dead center.  Using the timing
wheel it says I need to use the red shim (.008) and apply 20ft lbs
torque to get the suppressor index pin notch bottom dead center.  This
is what that looks like hand tight.



I've torqued the shit out of that Muzzle brake and not made much of an
improvement.  There is no way that is supposed to torque to bottom dead
center,right?  
The thinnest shim is purple at .003, the next thinnest is no color at
.005.  No color is just a little too far past bottom dead center.  I think if I had two purple shims it'd work out right.
Any of you guys put a Surefire muzzle brake on your rifle and does that
look right?  I've mounted two Surefire compensators on two different
guns for the FA556AR Suppressor and neither were that difficult to line
up.     HELP!
Hoping Kudu22 will chime in.

 

Looks to me like you need to reduce the shim by about 0.0044" (going by 1/8 of a turn the mount is off). I would pull off the .008 and put on the .005 and see how much torque it takes to line it up.

Did that, .005 is just a RCH past bottom dead center.  I think 2 purple shims at .003 each would get me at BDC with torque.  Problem is they only put one purple shim in the  kit with the brake and my two other kits left over shims aren't purple.  Looks like I'll be calling Surefire in the morning to send me a couple purple shims.  Damn it, I sooo wanted to mount and shoot this pig tomorrow, now I gotta wait another week.

Do you have the bevel on before any shims? I usually place the bevel, scew on the adapter (flash hider or comp) and then see how much I need to get to BDC before I start shimming. I have one flash hider adapter that missed BDC after rocksetting and it really makes no difference. It is about 3 degrees off.

Yeah, used the spacer with chamfer facing the barrel shoulder, tightened the brake hand tight, looked at the chart then used the suggested shim. NO go.  Then I tried every shim and combo I could think of to time it and that was a No go.  Closest to BDC was the .005 no color shim and it was a little off past BDC hand tight.  I'm fairly confident that .006 would put me right on, or close enough to it torqued.



Called Surefire Suppressor Div. yesterday and the rep suggested trying to time it without the spacer and said he'd get a shim kit sent.  I think I'll wait on the shim kit and try two purple shims to get .006.

Would like to know how this works out for you. Post an update if you can.

1 divided by 28 is .035. So .035 will set your mount back exactly 1 turn.  .009 will set the mount back 1/4 turn. Figure what you need then add to the barrel. Timing the mount is fairly easy if you know the pitch of the thread your working with.

I'm such a fucking Idiot.Thanks for your post.  Math is useful, who knew.   Don't know what I'd do without Arfcom.  The brake looks close enough, so I'll call it timed (green shim .020, blue shim.010, red shim .008 and none .005) but I'm sure there's still something I can fuck up.  Thanks guys for all the suggestions.  There doesn't appear to be any alignment issues, looks good down the bore and the cleaning rod went through without any snags, guess I'll degrease and Rocksett and give her a shoot in 24hrs.









 
 

Good luck!

Sorry that you cant shoot it, but How bout some pics?  I've never seen a FA556AR on a 12.5 with a FSB.

I'm using the FA556AR on a couple of different uppers with the CAM4FA556 adapter, so I would also be curious to hear what you think of the brake.

They're not great pictures but I guess they'll do.  Hopefully I'll get to shoot it and check Zero tomorrow at lunch.  I've been using the CAM4FA556 on the backup 16"AR and the CA556AR203 on the duty 11.5".    This 12.5" upper replaced the 11.5" for duty use.  






















 
 

Wow!  I feel an odd sensation in my pants

 

Thanks.  I get that odd sensation too surfing around these parts.





Went to the range today to check Zero.  Had to shoot quick and couldn't
go prone, the range was flooded.  At 50, Standing unsupported, zero appeared to have shifted  low just a little.  Supported on the trunk of
the car, much tighter group but still a little low.  The brake worked well,
mounted the suppressor and shot a few without issue, then went back to
just the brake.  After a quick 60 rounds I decided I like the brake.  It
controls recoil very well and made it easier to make good solid com
hits fast. It is loud,  that's ok, I like loud.  Going to shoot more
than a few rounds this Saturday and give it a good run.  I don't know
much about brakes, this is my first, but I think I'm going to like this
brake enough to buy one for the RRA.





Again, thanks for the help fellas.

Don't feel bad my mount and indexing wheel gave me fits too. Did the brake come with your can? I'm looking for some brakes but Brownells is not listing them.

No, the brake was ordered from Surefire.  The Suppressor originally came with CAM4556 flash hider.



 

I have 2 uppers with the cam4fa556.  I don't have any with the MB mount.

I'm really curious about the MB mount and how it compares to the "compensator" which is basically a modified A2.

Sorry brother I was at SHOT and didn't get into my accounts to check mail. Glad you got it worked out.

I realized after I posted that you were probably at SHOT and had your plate full.





 

No comparison.  The compensator is an adapter that hides flash very, very well.  The brake almost eliminates recoil.  I don't really know how to describe the recoil impulse but it's almost non-existent and allows for quicker follow up shots.  I'm sure the brake looks like a dragon breathing fire at night but with the suppressor mounted that should cut that out, I let you know when I get a chance to shoot it at night.  



I shot another quick 60 rounds today at lunch and let a partner shoot it and I think I've sold another couple of brakes for Surefire.  Our Captain was there too and now he wants one.  I don't know much about brakes, but from what I've seen with the 120 down the pipe so far, I think this one is worth the cash.