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Suppressors Need help indexing TBAC brake

BurnOut

BurnOut

DDOJSIOC
Full Member
Minuteman
Nov 24, 2013
1,826
797
Dallas
A few weeks ago, I picked up from MHS a Tooley/AINA barrel for my AIAT in .260 Rem, along with a TBAC CB brake with the appropriate threads. I sent the barrel to my cerakoter to get the factory AI "muzzle brake clamping area" coated black to match the rest of the barrel, and got it back the other day.

So, yesterday, I decided to thread the barrel into my rifle, and get the brake indexed... only to find that it's in the "sweet spot" such that it can't be indexed either without the peel washer installed (first pic below), or with the full/complete peel washer installed (second pic below). It seems that the coarseness of the AI muzzle threads along with the unidirectional nature (there is a definite top and bottom) of the TBAC brake have conspired to align such that I'll either need to stack an additional (partial) peel washer (NOT the way I want to go), or get someone to move the barrel "muzzle shoulder" back. Is there anything that I'm missing here?

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Hmm, going to ask a stupid question. But have you tried just part of a peel washer. If it is actually a peel washer. 1st photo looks like it went 1/8 turn to far, 2nd looks like it needs to go a little less than 1/2 a turn farther. If it is a true peel washer, split it in about 1/2.
 
It's not a stupid question at all... the issue that I am having is that because the TBAC brake threads on/off in full-turn increments (rather than half turn, like brakes that have no definite top/bottom), if I back it off of the "no washer" installation location almost a full turn (to get the top of the brake oriented where it needs to be prior to wrenching it into its final position), the gap between the mating surface of the back of the brake and the shoulder of the barrel exceeds the thickness of the peel washer. If I could get away with a half turn (like a SiCo, etc... brake), I'd be okay at a partial washer thickness.
 
Well then if i understand correctly you will either need to move the shoulder back or have a machinist (gunsmith) take a little off the back of the brake. by the looks of the first picture and the description in the video that .002 is about 17 degrees I am going to say that is about what you need. maybe .0015. Oh so damn close.
 
2ndamendfan said:
Well then if i understand correctly you will either need to move the shoulder back or have a machinist (gunsmith) take a little off the back of the brake. by the looks of the first picture and the description in the video that .002 is about 17 degrees I am going to say that is about what you need. maybe .0015. Oh so damn close.
Click to expand...

Yep... it is pretty damned close if I say so my damned self. It's the Goldilocks of situations... a few degrees one way or another, and I'd be okay. Grrrr.
 
Those peel washers come apart in super thin sections. I have not seen a barrel yet, that would not allow the brake to index. Weird
 
Ray, I haven't had a chance to mess with it yet. Hopefully tonight, if I can distract the wife long enough... ;-)
 
Would like to know solution. Bugs the crap out of me when people post an issue but never a solution. Happens about 95% of the time in the automotive forums.
 
I must have cooties or something... I can't get it where I need it. The AI muzzle threads (M18x1.5) threads are just too coarse to get me where I need to go without either moving the barrel shoulder back (or the back of the brake forward) or stacking another (partial) peel washer. This thing is like Goldilocks... :-/
 
Call the shop 307 287 2052 and we will send you a couple more. Maybe a full one and a couple layers is what you need.
 
Sorry hit reply to fast. With the M18 x 1.5 it sounds like the threads are a bit to coarse for you to get where you need.
 
So if i'm understanding this correctly and for everyone elses knowledge. The peel washer isn't thick enough to equal at least 1 revolution on a M18 x 1.5 thread which means there's a possibility that a single peel washer at any thickness will not index the muzzle brake.
 
FunkyTownScout said:
So if i'm understanding this correctly and for everyone elses knowledge. The peel washer isn't thick enough to equal at least 1 revolution on a M18 x 1.5 thread which means there's a possibility that a single peel washer at any thickness will not index the muzzle brake.
Click to expand...

That is correct. If I had another couple of thousandths off of the barrel shoulder, it would index perfectly without the washer. However, if I back it off (from its current position) to where it needs to index (the top of the brake at about the 10:30 position), the gap between the back of the brake and the barrel shoulder is larger than the (whole) peel washer is thick.
 
I had the exact same issue on multiple barrels - the same barrels in fact! Look at my post above. Buy a quantity of 3 packs or more so you will get some variety of thickness. It's a rather thorough kit. Problem solved.
 
Those won't fit. They only come it 1/2 and 5/8 inside diameter. His threads are M18 which is just a little smaller than 3/4.
 
FWIW, I ended up sending the barrel and brake to MHSA to have them move the shoulder (of the barrel) back and index the brake. I'm sure it would have been okay to use a full peel washer plus another partial one, but it would have looked odd to me. It's $75 I really would rather have not spent, but at least it'll look right.
 
I'm curious if TBAC has considered designing their brakes to be self indexing with a nut or similar design? I'm assuming it might take a longer thread spec on the muzzle to make some room though? Then we could do away with the peel washers.
 
Conrad said:
I'm curious if TBAC has considered designing their brakes to be self indexing with a nut or similar design? I'm assuming it might take a longer thread spec on the muzzle to make some room though? Then we could do away with the peel washers.
Click to expand...

Because of the perpendicularity tolerance requirements, you cannot rely on a jamb nut. It must be seated against the shoulder on the barrel. The jamb nut can and will cause cocking of the brake and consequently result in baffle strikes.
 
BurnOut said:
FWIW, I ended up sending the barrel and brake to MHSA to have them move the shoulder (of the barrel) back and index the brake. I'm sure it would have been okay to use a full peel washer plus another partial one, but it would have looked odd to me. It's $75 I really would rather have not spent, but at least it'll look right.
Click to expand...

I agree I have 2 that use an abnormal amount of shims and they look like shit. But I am not anal enough. I also cringe when having to give something to a smith that they will fuck it up. Been screwed over before.
 
2ndamendfan said:
I also cringe when having to give something to a smith that they will fuck it up. Been screwed over before.
Click to expand...

I hear ya... but I am confident that between the fact that I bought both the barrel and the brake from them, along with the fact that MHSA is a stand-up shop, that if anything goes wrong they'll do right by me.
 
quicklx said:
Because of the perpendicularity tolerance requirements, you cannot rely on a jamb nut. It must be seated against the shoulder on the barrel. The jamb nut can and will cause cocking of the brake and consequently result in baffle strikes.
Click to expand...

Okay, thank you. That is good information to know. I'm running a jamb nut on one barrel because the muzzle was threaded long specifically for a brake that uses a jamb nut. I just re-used the nut to take up the thread space for the CB brake. It sounds like I should consider myself lucky, and should not run the Ultra7 on that barrel until I have the muzzle threads redone. Thanks again.
 
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