Bore for 308 muzzle brake/Compensator?

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L1A1Rocker
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Bore for 308 muzzle brake/Compensator?

Post by L1A1Rocker » Sat Aug 23, 2014 6:45 pm

What's the word on bore diameter for a muzzle brake/compensator for 7.62 Nato and 300BLK?

I know the general rule for silencer clearance is .060 over but does that hold for compensators also? I was thinking it might be a bit tighter.

Anyhow, thanks for any input ya'll can give.

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Re: Bore for 308 muzzle brake/Compensator?

Post by Bendersquint » Sat Aug 23, 2014 8:28 pm

L1A1Rocker wrote:What's the word on bore diameter for a muzzle brake/compensator for 7.62 Nato and 300BLK?

I know the general rule for silencer clearance is .060 over but does that hold for compensators also? I was thinking it might be a bit tighter.

Anyhow, thanks for any input ya'll can give.
The more concentric the bore, the more accurate the threading and the tighter the tolerances the tighter you can make the bore.

How precise can you machine, once you answer that you can know how much tighter you can make the bore.

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Re: Bore for 308 muzzle brake/Compensator?

Post by john.t.little1 » Sat Aug 23, 2014 10:19 pm

Almost finished with mine did .350 just because that's the same size I made my can. Here's a link a friend sent that has info on brakes. http://rvbprecision.com/shooting/advent ... rakes.html

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Re: Bore for 308 muzzle brake/Compensator?

Post by Capt. Link. » Sun Aug 24, 2014 9:12 am

L1A1Rocker wrote:What's the word on bore diameter for a muzzle brake/compensator for 7.62 Nato and 300BLK?

I know the general rule for silencer clearance is .060 over but does that hold for compensators also? I was thinking it might be a bit tighter.

Anyhow, thanks for any input ya'll can give.
Set your barrel up in a four jaw centered and attach device.Bore it to to +.020 over barrel bore size .308+.020=.328 increase clearance if you see negative accuracy changes though doubtful.
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Re: Bore for 308 muzzle brake/Compensator?

Post by McLarenross » Sun Aug 24, 2014 10:10 am

Ill weigh in on this since I just did a muzzle brake attached 308 suppressor. I bored the brake to 0.340' and the baffles to 0.360". That seemed to be the most logical sizes given the roles of the two items.
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Re: Bore for 308 muzzle brake/Compensator?

Post by L1A1Rocker » Sun Aug 24, 2014 11:09 am

Hey there folks. Thank you all VERY much for weighing in on this. Some very good advice that I'll be taking to heart.

john.t.little1, that's B-E-A-utiful! And very close to what I'm shooting for. McLarenross helped me out a while back with a solid works rendition of some sketches I did for a muzzle device. Right now I'm doing a prototype in delrin to see how this process is going to go before I jump in with metal.

Again thank you all for your input, this is such a great place for minds to meet!

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Re: Bore for 308 muzzle brake/Compensator?

Post by john.t.little1 » Sun Aug 24, 2014 11:41 am

Thanks man it took a few try's to get right. Double start 10 stub acme threads were the pain. I'd already made my suppressor end cap threads so I had to make to match it. Got some mill work to do and they will be done. If you have any other questions let us know..
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Re: Bore for 308 muzzle brake/Compensator?

Post by L1A1Rocker » Sun Aug 24, 2014 1:31 pm

john.t.little1 wrote:Thanks man it took a few try's to get right. Double start 10 stub acme threads were the pain. I'd already made my suppressor end cap threads so I had to make to match it. Got some mill work to do and they will be done. If you have any other questions let us know..
Wow, talk about being on the same page. I'm planning on double start stub ACME at 8 pitch. Great minds must think alike after all. :lol:


Another question I'd like to toss out the the group: I was thinking about getting a reamer to finish out the bore for the muzzle device and the baffles. Then I was thinking about an adjustable reamer so I can dial in the exact diameter I wanted. But now I'm just thinking about using a plain old HSS drill bits. What are ya'll thoughts on the matter?

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Re: Bore for 308 muzzle brake/Compensator?

Post by john.t.little1 » Sun Aug 24, 2014 6:45 pm

I have used the adjustable style before and I don't care for them I don't know if the style I used is diffrent from others out there but I had a hard time making sure it was tight and keeping the correct size. And on top of that it had a slight taper to it. I ordered my reamer from bass tool it's hss and works fine. Use drill bits but reamers give a more round hole if that makes sense. If your brake doesn't thread into your cap don't be afraid to cut the threads deeper. I used a 16er insert tool holder and found a 16il internal threading tool so I could use same inserts plus it's nice being able to start from inside and not worry about crashing unless you put your worm gear in reverse like I did the first time.
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Re: Bore for 308 muzzle brake/Compensator?

Post by wp6529 » Fri Aug 29, 2014 9:19 am

If the adjustable reamer you used had a little setscrew in the tip, it was not a type that is adjustable in the way you were thinking. That type is only adjustable in the sense that the screw lets you expand it a bit so that it can be reground to the original size.

The blade type adjustable reamers that have a set of blades held between two nuts are they type that is actually adjustable to different sizes as the back of the blades and the mandrel are tapered so as you adjust the nuts the blades will move in/out while remaining parallel.

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Re: Bore for 308 muzzle brake/Compensator?

Post by Dr.K » Fri Aug 29, 2014 5:25 pm

Also, when I delved into making a muzzle device, I studied some brand name devices.

I noticed on some of the more effective ones, that the first hole(s) were a bit larger than the following holes, so that some gas could actually go past the first baffle and work against the second or third baffles of the device.

I would make sure the final hole was nice and tight though!
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Re: Bore for 308 muzzle brake/Compensator?

Post by john.t.little1 » Fri Aug 29, 2014 8:46 pm

WP it was the kind with a set of blades and nut at top and bottom
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Re: Bore for 308 muzzle brake/Compensator?

Post by Hard_ware » Thu Sep 11, 2014 12:10 am

Dr.K wrote:Also, when I delved into making a muzzle device, I studied some brand name devices.

I noticed on some of the more effective ones, that the first hole(s) were a bit larger than the following holes, so that some gas could actually go past the first baffle and work against the second or third baffles of the device.

I would make sure the final hole was nice and tight though!
Muzzle brakes I have used are like that as well.

Larger hole near muzzle, slightly smaller in middle chamber, and smaller farthest from the muzzle.
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