Muzzle Brakes, chamber or not?

[Alex Wheeler]

I am wondering if anyone has done any testing for accuracy with different muzzle brake designs? Mostly the Harrell's type used on most light guns. I am concerned with any advantage of opening them up so they have a "chamber" or leaving the whole bore just over bullet diameter?

 

[stool]

the brake bore needs to be close to gun bore with or with out a chamber...
so you have me confused

 

[DennisH]

The brake bore standard is .020 over the bullet.

Example: .308, the break bore should be .328 .

Dennis

 

[Alex Wheeler]

Right, but I have had them where the inside of the brake is opened up to about 1/2" and only the end is .020 over bullet diameter (chamber), and I have had them where the whole brake .id. is .020 over bullet diamteter (no chamber).

 

[Preacher]

I have opened up a lot of them for a chamber, usually to 5/8th and never noticed any disadvantage's..
They shot as good as the straight .020 over bore diameter....
They did seem to reduce recoil a bit more....

 

[stool]

having never built or tested one, the basic principle is that some of the gas following the bullet needs to be redirected and its energy absorbed in a different direction. a chamber does that, a hole/port does it on a smaller scale. lots of holes equal how big of a chamber.
if the holes and the chamber are both round i see no big diff. if the chamber has a flat side for gas impact, it should work better than a hole that really only has a small surface that is truely redirection gases.
keeping the bore dia as small as practical will strip off more gas.

 

[Steve Blair]

The most efficient brakes, found on lightweight or vehicle mounted howitzers, are large, open chamber designs. For various reasons, they are not the best choice for most small arms. An antechamber, constricted to a diameter just larger than bullet diameter at the forward end, will improve the capture ratio and efficiency, provided the ports are large enough to permit free gas flow.

 

[stool]

the 50 bmg clam shell brake is very good...but there is only one place to be..directly behind the rifle.
all else gets blasted.
90 degree ports/holes/chambers are more "other shooter" friendly....less disturbing to others.

i shoot a shrewd's (brownells)on a couple of my rifles..i can afford and install them, they work. are they the best..i doubt it.

but the price seems to really climb once you get past the shrewd.......

 

[Ackman]

I don't for a moment think that bore dia. must be only .020" over bullet diameter. The brake on most of my rifles is a big heavy thing, 4" long. Has a large chamber leading to several step downs, 130 small holes radially. Some very savvy people used a bunch of expensive computer time arriving at this design. They're very effective. The hole in the end is .330"......considerably over .22 cal bullet dia. I also have another more conventional design which works really well too and the muzzle in that one is also .330". I have a couple Harrells brakes....very well priced, as yet unused.....the muzzle hole is a much smaller .250"...... unfortunately the radial holes were drilled last and burrs inside weren't cleaned up, they're so large a .224 bullet won't go through. These things are gonna' take some work.

 

[Steve Blair]

The attached picture is what efficiency looks like. Note the very high ratio of diverted gases versus those following the projectile. Designers of howitzer brakes have some of the same concerns as small arms brake designers. If the brake diverts gas too far rearward, it will cause crew problems. If diverted downward or asymmetrically, gas will cause dust or stability problems. [br]
This picture is an M777 Lightweight 155mm howitzer firing at high elevation and heavy charge.

 

[stool]

GO LOOK AT A THING CALLED LAMINAR LAYERS.
close is better.
big hole means the gas next to the bullet is untouched....330 for a 224 bullet is not EFFICIENT.

does not mean it will not work, just not as well as smaller....

another concern might be gas accelerating forward of the bullet with such clearance....possible upsetting the bullet ??

I don't for a moment think that bore dia. must be only .020" over bullet diameter. The brake on most of my rifles is a big heavy thing, 4" long. Has a large chamber leading to several step downs, 130 small holes radially. Some very savvy people used a bunch of expensive computer time arriving at this design. They're very effective. The hole in the end is .330"......considerably over .22 cal bullet dia. I also have another more conventional design which works really well too and the muzzle in that one is also .330". I have a couple Harrells brakes....very well priced, as yet unused.....the muzzle hole is a much smaller .250"...... unfortunately the radial holes were drilled last and burrs inside weren't cleaned up, they're so large a .224 bullet won't go through. These things are gonna' take some work.

 

[Preacher]

Any thing much over .020 over bullet diameter will cause accuracy problems, sure the larger holes will work but just not as well...
Ran one of my 6br's at .020 and increments of .010 larger until I got to .045 over and it was plain to see it was causing problems the larger the exit hole was....

 

[Ackman]

GO LOOK AT A THING CALLED LAMINAR LAYERS.
close is better.
big hole means the gas next to the bullet is untouched....330 for a 224 bullet is not EFFICIENT.

does not mean it will not work, just not as well as smaller....

another concern might be gas accelerating forward of the bullet with such clearance....possible upsetting the bullet ??

Gas is behind the bullet, then it goes out the holes. And these things I use work better than "well." But who wants to argue with internet experts.

 

[Ackman]

Any thing much over .020 over bullet diameter will cause accuracy problems, sure the larger holes will work but just not as well...
Ran one of my 6br's at .020 and increments of .010 larger until I got to .045 over and it was plain to see it was causing problems the larger the exit hole was....

Accuracy problems.....no. None at all.

 

[dkhunt14]

I agree with what preacher says and was told by a really smart guy that if a brake doesn't have a wall to help divert gases it doesn't work well. Another shooter I know makes a brake with various chambers or step downs and that brake is the best at recoil reducing that I ever shot. It makes a 17 pound 300 WSM seem really tame. Matt

 

[dkhunt14]

Maybe Joe Salt will chime in because he has one of the multi stepped brakes by this gunsmith. Matt

 

[Joe Salt]

Yes Matt the brake made me a sissy I always shot without breaks because I thought they didn't help accuracy, because I seen guys take them off to shoot in HG. class before our rule change, and the rifles shot tighter groups, so I believe if the brake isn't built right it will hurt accuracy. I haven't tried mine without it yet but I just may try it. [Hope it doesn't hurt]

Joe Salt

 

[Alex Wheeler]

Thats interesting. What are the requirements for an accurate brake?

I am picturing this stepped brake in my mind and can see how it would help having multiple walls to stop the gas. I like it.

 

[Alex Wheeler]

Tom does the brake on your Brux have a chamber in it?

 

[Alex Wheeler]

Did Knapp leave the whole id .020 over or did he hollow it out inside?