Timing a muzzle brake/comp

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dakota.potts

New member
I recently bought a Manticore Nightbrake for my PTR barrel that I'm using for my CETME/G3 build. The brake looks to be of good quality and has a retaining spring to keep it locked down when tightened. The problem is that, when it's twisted on snug to the point where the retaining spring catches, it's not indexed properly. It's maybe 20-30 degrees canted.

I assumed this can be timed by some sort of shim or washer mechanism? Are there shims or washers sold for this, or is it something I would need to turn myself on a lathe? Do I just time it where I want it and then measure the gap between the brake and the shoulder on the barrel?
 
Is the washer on the brake, or separate? You should be able to take a thousandth or so off the brakes shoulder, to get it to come on around. You can calculate close to the correct amount, by the brakes angle, and the threads per inch. If it is 1/4 turn, or 90 degrees, from where it's needed, then divide the distance between one thread by .25, and that will give you the amount. Cut shy of that, so it will tighten. That, or just take a little off at a time until you get it.
 
From their website:

A total of eighteen ports distributed around the upper 270 degrees of the device help stabilize and reduce exiting gas pressure. There are no ports facing directly upwards to allow for an uninterrupted sight picture when firing, and the lower 90 degree arc has no ports to prevent a dust signature when fired. - See more at: http://www.primaryarms.com/ma-1214/p/ma-1214/#sthash.VfEVFojj.dpuf
Click to expand...

Maybe my synapses aren't firing correctly, but that makes no sense to me. First it says all porting is on the upper 270 degrees, then it says there is no porting on top...

Anyway, I install several brakes a week on average. Notwithstanding some feature on this I'm not getting that allows it to be timed- it needs to be a crush washer or lathe work if you don't want to use one.

Crush washers are made to use on factory threaded barrels. Because I do the threading, it comes down to setting the shoulder back on the barrel, or turning a bit off the back of the brake if possible.

Like Dixie said, it's a game of .001's... A 24 pitch thread equates to roughly .042 of shoulder or brake per full revolution. If it's a round brake that's easy to chuck, I'll put it in my smaller lathe and turn off the back of the brake until it times. This is a real PITA...it's very difficult to get it on the money, and some brakes make timing more visible than others. One or two degrees certainly isn't going to affect the brake's effectiveness- but can be visible. On these, I'll make witness marks and take measurements. "About 1/4 turn" doesn't cut it. Thread crush on tightening, in my experience, is about nil as far as getting another degree or two. One thing to get a thousandth on headspace with crush when tightening a barrel, this is different. When you hit the shoulder, that's it...

Take off too much shoulder and over-rotate, and then you're back to taking nearly a full revolution more off the shoulder.
 
By looking at the photo of the brake, it looks like about a 30-45 degree division of the cylinder has no holes for the bottom, but the rest does. They say it's to help prevent muzzle rise, but with all the holes down the sides, I wounder how much that actually helps? Generally, a brake used to stop muzzle climb has the holes mainly along the top, so the gas vents upwards.
 
Go to precisionarmament.com and order their accu washer alignment system. This could possibly solve your problem.
 
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