Question about the ID of Muzzle Brakes.

[jackieschmidt]

Concerning the ID of a standard muzzle brake, is the ID .020 or so over the bullet for the full length ,or only the last portion.?

 

[rickiesrevenge]

.020-.030 for the whole length is pretty normal.

 

[Cloudrepair]

It seems it would work the same if it was only last .5 or so

 

[gunsandgunsmithing]

Jackie, it'll work both ways. There are commercial brakes out there that are actually pretty good, that have a .224 exit but are nominally .300 through all but the end. Of course they are meant to be gunsmith installed and opened but I've tested lots of brakes..and made several, and I'm not sure you could even measure the difference in how they work, in this regard...much less "feel" the difference. Some have what they refer to as expansion chambers and some don't. The most important factors in regard to how much they reduce recoil is two things, sail area and location of the first baffle. Not saying other factors don't matter, cumulatively, but those are the biggies.

 

[jackieschmidt]

My main concern is does any particular way affect accuracy one way or another.. I kinda threw one together to go on my 308 project, nothing fancy, and while it cut down on recoil substantially, accuracy is not up to expectations. The hole is .030 over and straight. It does seat against the counter bored crown rather than the shouldering on the barrel OD.

I checked it in the lathe on the barrel and run out was only around .002.

I have always felt that any rifle I built with a top quality custom barrel should be able to shoot 5-shot groups at 1/2 inch or better. This one won’t. I’m limited on components, I have Reloader 15, 2495, and 4895, but the only bullets I have are Speer 168 match bullets and Federal primers.

I took the brake off and it did shoot at about a .600 level, but recoil pretty rough on this hunting weight rifle.

 

[Jesswil61]

Jackie,
I am definitely not the expert that some are here however, I have played with seating brakes on the face of the counter bore as well as opening up a gap and seating on the barrel OD and the latter has seemed to have the best result. I am sure there is someone here who can provide a differential explanation. I believe shouldering on the barrel OD has less of an impact on barrel harmonics compared to seating at the crown area.
Jesse

P.S. I am working with a Browning in 308 win. that I added a BOSS system brake that I cannot seem to make shoot as well as I would expect. Let me know if you find the magic fix!

 

[WayneShaw]

I fitted a Harrells brake for a friend not long ago. I have always bored the brake ID thread diameter to the last exit hole, then bored to .020" over bullet. This time I did a little math. I computed the angle from the first row of exit holes to the last one, set the compound there and bored the inside on a taper that started at full diameter at the first row and ended right at the bottom of the last row, then bored the exit hole to proper diameter. Looked great!!!

 

[Alex Wheeler]

Jackie,
I dont think your brake is the issue. I have bored them .020" over the whole way, put in chambers so only the end was .020 over, as well as other things like cones ext. All of them have shot very well. On magnums I will go .030 over because that first port can constrict due to the heat all that powder volume has. 308s shoot quite well, Id suspect the bullet first then the barrel if you have checked all the normal stuff like bedding and scope.

 

[jackieschmidt]

Jackie,
I dont think your brake is the issue. I have bored them .020" over the whole way, put in chambers so only the end was .020 over, as well as other things like cones ext. All of them have shot very well. On magnums I will go .030 over because that first port can constrict due to the heat all that powder volume has. 308s shoot quite well, Id suspect the bullet first then the barrel if you have checked all the normal stuff like bedding and scope.

Alex, I have a PTG bolt coming. This factory bolt is a piece of crap. The handle is out of time, and firing pin hole has about .010 clearance. Plus, the spring is all waded up and rubs. I figured by the time I messed with this one, I could just get a PTG. Carlsbad has one headed my way.

I took the flutedbarrel off and chambered up a 1-11 twist medium Palma Krieger, which matches the Remington Varmint Taper pretty close.

I rough drilled and threaded up a new brake tonight, left it on the stub so I can put it in my dividing head tomorrow at my shop and drill it. I made the thread .700 28tpi.

i am going to seat this one on the barrel OD shoulder. Tomorrow night I will remove the barrel, rethread it for the .700 28tpi, and finish it up.

 

[jackieschmidt]

I fitted a Harrells brake for a friend not long ago. I have always bored the brake ID thread diameter to the last exit hole, then bored to .020" over bullet. This time I did a little math. I computed the angle from the first row of exit holes to the last one, set the compound there and bored the inside on a taper that started at full diameter at the first row and ended right at the bottom of the last row, then bored the exit hole to proper diameter. Looked great!!!

That sounds like a neat idea.

 

[DaveTooley]

It's been my experience that a brake with an expansion chamber is more efficient than one with a smaller bore diameter. But if the length of the chamber exceeds about 1.250" accuracy will suffer. The length allows gas to pass the bullet thus upsetting it somewhat. Exit gasses have an initial velocity of 6-8K FPS. I make my exit holes .040" over bullet diameter. All the work has been done by the time the bullet exits. I've seen carbon build up to the point of contacting the bullet.

 

[AlNyhus]

Jackie, I'd try a known-good flat based BR style bullet before doing anything else. I use 150's made on J4 1.150 jackets to test hunting-style .30's for accuracy before substituting a traditional hunting bullet. I'd be happy to contribute some to your project, if you like. -Al

 

[Rob01]

Being larger than .020" over is not an issue. I have run .30 brakes on 6mms and they are very accurate. Actually have a .338 suppressor adapter on a 6.5. Again very accurate. If accuracy isn't there I would look elsewhere.

 

[jackieschmidt]

Jackie, I'd try a known-good flat based BR style bullet before doing anything else. I use 150's made on J4 1.150 jackets to test hunting-style .30's for accuracy before substituting a traditional hunting bullet. I'd be happy to contribute some to your project, if you like. -Al

Al, due to the fact nobody can get anything at this time, I’m working with what I have on hand.

 

[jackieschmidt]

It's been my experience that a brake with an expansion chamber is more efficient than one with a smaller bore diameter. But if the length of the chamber exceeds about 1.250" accuracy will suffer. The length allows gas to pass the bullet thus upsetting it somewhat. Exit gasses have an initial velocity of 6-8K FPS. I make my exit holes .040" over bullet diameter. All the work has been done by the time the bullet exits. I've seen carbon build up to the point of contacting the bullet.

Thanks, Dave. I think I will incorporate a tapered chamber that Shaw untilized.

 

[AlNyhus]

Al, due to the fact nobody can get anything at this time, I’m working with what I have on hand.

The gun might be better than it's showing you, Jackie. A known-good bullet will prove it one way or another. Re15 and H4895 are both good powders that should show you something in a 308.

That 168 Speer Match has always been so-so for accuracy in any .30 I've tried them in. The Sierra 168 Match has always been better...though they aren't all that great, either.

Good shootin'. -Al

 

[butchlambert]

Jackie, I acquired a used Obermeyer 1-11.25 twist 30" Palma barrel. I had it contoured to a #4 Shilen taper and cut it to 22". I've had best luck with the 168 grain Sierra Match and 185 Berger Hybrid Target. I don't have a brake and the 185s hurt. They are stable in the 11.25 twist.

 

[jackieschmidt]

I put the brake on tonight, came out good.

I hope to have my PTG bolt tomorrow or Friday, I will probably have to set the barrel up and adjust the headspace. I’m not sure how close PTG keeps theirs to the Factory dimensions.

 

[KMart]

Al, due to the fact nobody can get anything at this time, I’m working with what I have on hand.

PM sent

 

[Will Henry]

I have always made my brakes with an expansion chamber and bored the front to around .020 to .025 over bullet dia. I have always seated on the shoulder. Typically, for a 30 cal., the chamber is .406 and the front is .328 ID. Four circles of six holes. A variation on this was to drill at .406 all the way through then thread the front to 7/16x32 to accept an insert which was bored to .020" over bullet diameter. I had a reason for doing this but don't recall what it was!
I have always felt, if a 308 won't shoot 1/2 moa or better, with 41 of 4895 and a 168 Sierra, there is something wrong with the rifle. 168 Lapuas are at least as good. WH