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Converting .223 Compensator For Use On 9mm Subgun


StealthyBlagga

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I have a 9mmPara MAX-11 subgun upper on my M11/9. I would like to experiment with using a compensator, but the thread on the barrel is 1/2-28 like on a .223 AR15 barrel. I have an old .223 compensator I would like to try, but obviously I will have to open up the holes for the larger bullet; can anyone tell me the optimum hole size ? If I'm careful, can I drill out the holes on a drill press, or should it really be done on a lathe ?

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Setting it up on the lathe is a good idea, but I suspect that it will be overkill. Personally, I would just take it to 3/8" on the drill press and then try it out. That will only give you 0.010" bullet clearance. If the bullets put marks on the suppressor (hits it), go up to 25/64", which gives you 0.018" clearance. Keep going until the bullet doesn't touch. You want the clearance kept small to make the most of the gas that you have.

Frankly though, I would not expect a whole lot out of a brake on 9mm factory ammo. Now, if you handload light bullets with large charges of slow powder and rifle primers (9mm Major Open Gun ammo) you will have more gas to make the brake work.

Billski

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I'd definately do it on a lathe. The .010 is a good place to start. I'm not familiar with the setup you're using, is it an open bolt? If so, I don't think a comp will have much effect. A suppressor, on the other hand works nicely :)

Yes, its an open bolt gun... why would this affect the compensator's effectiveness ? I assume the bolt stays closed until after the bullet has left the barrel, so I won't be losing pressure out the breach, will I ? I'll probably use factory 115grn ammo, so pressure will be OK but not stellar. Barrel is 8", so I'm thinking pressure will still be pretty high compared with a 16" carbine.

I don't have access to a lathe, only a home drill press (not that precise a one either), so I'm leaning towards allowing more clearance... better safe than sorry.

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The bolt, since it's not a locked breach system is heavy. The weight of the bolt simply holds the case in the chamber for a time that is determined by the weight. Fired at night, you might see almost as much flash out the ejection port, as you do the muzzle. It's just a blowback action, with high pressure working it.

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I just checked the comp on my 9mm. The exit hole is .366", which gives .011" clearance. If your comp's exit hole is centered in the body, you may get good results with a drill press. Otherwise, you will likely have to go a bit larger to avoid getting bullet strikes.

I have an M11 set up in a TASK-style slowfire. The comp does help some, but to be honest, it's not really needed. The gun shoots very flat, even with the comp removed.

The MAX-11 seems a little muzzle-heavy. It made the gun feel more like an Uzi than a slow-fire M11. Not quite as smooth, but still exceptionally controllable. I'd have bought a MAX-11 if I hadn't already drilled my receiver for a slow-fire conversion.

BTW, which AR brake are you going to use? A handgun comp with ports on top would probably be more effective than a rifle brake with vents on the sides. Something to think about. I don't think you would have too much trouble getting a pistol comp threaded in 1/2-28.

As Dan said, a suppressor works very well to control recoil / muzzle climb as well. However, you do get a lot more smoke out of the ejection port, and it speeds up the gun somewhat (probably not a problem with your upper).

DSC01848.jpg

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BTW, which AR brake are you going to use?

Its a Cavalry Arms "CavComp like this:

cavcomp.jpg

Its basically styled after an A2 flash hider, but has a closed muzzle to form a single expansion chamber with exhaust ports at 3, 9 and 12 o'clock. I was hoping it would work OK as it is closer in design concept to a pistol comp than a rifle comp.

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