Barrel crowning and muzzle brakes?

[Ih8sks]

First of all apologies if this is in the wrong forum. Couldn't decide if this question should be posed here or in the target shooting forum.

I was thinking about this lately and wondering what the relationship between the two is? I know (or have been lead to believe) that for a non threaded barrel the shape of the crown can have an effect on the accuracy of the barrel. Then I was thinking if you were to add a muzzle brake now to the same barrel is all that effect of the crowning thrown out the window? The crown is there to direct the exit gases in a certain pattern as the projectile leaves the barrel, and a muzzle brake does the same thing although for a different purpose.

The question(s) I'm wrestling with are:

1) If you're going to be running a break anyway is there any need to have a specific barrel crown?
2) or is there a specific barrel crown that compliments/enhances the effects of the muzzle brake?

I was thinking about this because of a build I'm considering and thinking about if it's worth the extra work to have the barrel crowned if it's going to also be fitted with a brake.

Has anyone else ever given thought to this?

 

[tiriaq]

There are different ways to finish the end of the bore and muzzle. Assuming machining is accurate, it doesn't seem to make much difference which is used.
Yes. a muzzle should be properly finished, brake or no brake.
No idea if one pattern works better with a brake than another.
Personally, I prefer to set the barrel up in the lathe, and take a pass across the muzzle at 90 degrees, and break the sharp edge. I then take another pass, counterboring the muzzle slightly. Recessing the end of the bore protects it. I then finish the edge of the bore with a piloted hand cutter. Just break the sharp edge. I finish a muzzle this way brake or no brake.
If I am finishing a muzzle without using the lathe, I have a Brownells hand crowning set. Using piloted cutters, the muzzle is faced square and then 11 or 45 degree cutters are used to finish the bore with a slight chamfer.

 

[guntech]

I finish all of my muzzles with a piloted chamfer reamer as shown in this picture of a recessed crown... All the different crown are for looks as much as anything... I don't think anyone pokes the muzzle in the dirt intentionally and no crown would be protected from that. The most important thing is the transition from the bore... it needs to be concentric to the bore and burr free...

 

[Ih8sks]

I finish all of my muzzles with a piloted chamfer reamer as shown in this picture of a recessed crown... All the different crown are for looks as much as anything... I don't think anyone pokes the muzzle in the dirt intentionally and no crown would be protected from that. The most important thing is the transition from the bore... it needs to be concentric to the bore and burr free...

So in your experience/expertise no performance difference between a recessed crown like the example above and the 12 degree dished target crown that seems to be popular on bull barrels?

 

[Randy B]

The benchrest crowd overwhelmingly shoot a barrel that is just faced off square. And these guys arguably shoot some of the most accurate rifles in the world.. A recessed or champhered crown offers some protection from bumps.

 

[bearhunter]

IMHO, I would be more concerned about the brake than the crown.

Guntech tells it in plain easily understood terms. 90 degree concentricity, with sharp edges, to the axis of the bore is paramount. Like him, I finish all of the crowns I cut in a similar inlet type fashion.

I don't use a piloted tool, but it certainly wouldn't harm anything.

For me, it's the brake that really concerns me.

So many negative issues can be induced into barrel with the addition of a brake.

Brakes change harmonics drastically.

If the brake isn't absolutely true to the axis of the bore, accuracy is seldom stellar, although it may be acceptable for hunting purposes.

Another issue I personally have with brakes, is that they often have a long expansion chamber just after the muzzle, that is far to large in diameter.

The excessive inside diameter of the expansion chamber allows gasses that should be deflected through the ports to pass the bullet while it travels through it and can/does cause negative influences to the bullet as it enters the exit port. This is really noticeable on very accurate rifles with bore twist that barely stabilize the bullet.

If the threads are cut so the fit between the brake and barrel is to tight, stresses can also be induced. Likely minimal and for most sporting rifles, not a concern.

For the above reasons, I don't thread the brakes I make up for my rifles. I silver solder them on instead by making up a copper/brass spud that fits the bore of the rifle snugly as well as the bore of the brake.

I don't cut an expansion chamber, I bore it with .002 in clearance all the way around the exiting bullet diameter.

This has a couple of very good advantages, it allows minimal gas leakage around the bullet and maximum gas diverted to the ports, which decreases felt recoil noticeably better and doesn't affect accuracy.

It also makes cleaning the brake very easy. Just clean it the same way as you clean the bore, at the same time.

The other really big advantage, again IMHO, most commercial brakes, with large expansion chambers and small exit holes will actually get a build up of residues, just inside the lip of the exit hole.

I've seen this condition on several rifles, to the point it affected accuracy severely.

This build up can be very difficult to clean up.

When I first heard what I mentioned above, I was skeptical. I was wrong.

Most commercial brakes have overly large bullet exit openings for a good reason. To slow down or eliminate the issue I listed. They work OK but aren't nearly as affective as they could be.

 

[guntech]

I don't cut an expansion chamber, I bore it with .002 in clearance all the way around the exiting bullet diameter.

Is that a typo? 2 thou? I think you meant 20 thou... .020... ?

 

[bearhunter]

Is that a typo? 2 thou? I think you meant 20 thou... .020... ?

Nope, .002 over the diameter of the bullet that exits the muzzle.

I wanted to deflect the maximum amount of muzzle gasses out of the ports as possible, rather than allowing them to create turbulence around the bullet while it's in the brake.

I've only made up a half dozen of them and presently only have one rifle with one of the brakes I make up. A sported 7X57

I also only cut ports on each side, in a channel, all in a row.

The .020 you are referring to, can lead to all sorts of issues, if there is a large expansion chamber.

I wanted to eliminate those issues and make cleaning part of the bore cleaning process, along with making the brake very effective.

My brakes are long, at least 3.5 inches.

I can fully understand why people don't like them that long.

The only reason I started making my own brakes was because of shoulder surgery and I needed something that I could hunt with, that wouldn't create to much stress on the healing cut.

I don't like brakes on my rifles, for all sorts of reasons, but again, I can fully sympathize with anyone that's recoil shy.

I have to shoot this rifle when I have the range to myself. The muzzle blast deflected through the ports is vicious. It will knock over tripod mounted scopes on the next bench, a couple of feet away and clear off any papers or targets on the adjoining benches at out range, which are very close together.

 

[Potashminer]

So in your experience/expertise no performance difference between a recessed crown like the example above and the 12 degree dished target crown that seems to be popular on bull barrels?

I do not compete, nor have I built target rifles. But theory that seems to make sense is as mentioned several times - the edge of the grooves and rifling - of the bore - that lets go of the bullet - the last contact point - must be even all the way around the bore. I have a hand piloted muzzle crown tool with various angle cutters. When pilot is snug sliding fit into bore, I have seen many times that the first cutting is not concentric to outside of the barrel - in other words, that bore is not perfectly centre within the diameter of the barrel end - so the muzzle needs to be squared off to the bore - not necessarily to the outside of the barrel. I have two Schultz and Larsen target .22 rifle here - no doubt 40 years old plus - but both have perfectly "flat" or "square" faces to their muzzles - so presumably perfectly square to the bore - with just tiniest relief visible on the tips of the rifling - can no longer see that fine with my old eyes, but fairly apparent with magnify glass. After this many years, it could be erosion wearing away the rifling tips, but I think they were cut that way.

I also recently received a Schultz and Larsen "target" barrel - 30 caliber, 1-14" twist - I believe was for PALMA style shooting with aperture sights. The muzzle is dead flat, with a noticeable bevel taken into the rifling - much like the muzzle pictured above.

 

[guntech]

So in your experience/expertise no performance difference between a recessed crown like the example above and the 12 degree dished target crown that seems to be popular on bull barrels?

If the bore is not perfectly concentric with the diameter at the muzzle you will notice that when machining the end of the barrel... the machining should be centered on the bore and the cutting done outwards... then the 'wobble' is at the outer diameter and will have less effect on the crown. If it is a 90 degree flat crown the 'wobble' or run out is less visible. Finishing the bore with a piloted chamfer makes it edge of the bore perfect. Accuracy wise it would be hard to distinguish accuracy differences in styles of crowns if the edge of the bore is concentric and burr free. The 60 degree chamfer also protects the crown in that there is no 90 degree sharp edge left which is easily damaged in cleaning. I think you could cut a barrel off with a hacksaw and simply finish the bore with the piloted 60 degree reamer and it would shoot just fine and look like hell...

 

[Leeper]

When installing a brake, I like to have the muzzle flat with the 60 degree bevel to break the edge as Guntech has shown. FWIW, I like expansion chambers and cut bore the muzzle of the brake to give .010 clearance. I have not seen any issue with accuracy after the installation of the brake. Most shoot better; probably because they are easier to shoot.

 

[bearhunter]

If the bore is not perfectly concentric with the diameter at the muzzle you will notice that when machining the end of the barrel... the machining should be centered on the bore and the cutting done outwards... then the 'wobble' is at the outer diameter and will have less effect on the crown. If it is a 90 degree flat crown the 'wobble' or run out is less visible. Finishing the bore with a piloted chamfer makes it edge of the bore perfect. Accuracy wise it would be hard to distinguish accuracy differences in styles of crowns if the edge of the bore is concentric and burr free. The 60 degree chamfer also protects the crown in that there is no 90 degree sharp edge left which is easily damaged in cleaning. I think you could cut a barrel off with a hacksaw and simply finish the bore with the piloted 60 degree reamer and it would shoot just fine and look like hell...

That's why I make up a brass spud, with the internal diameter of brake and barrel when I fit them together. Easily pulled or driven out after everything cools. Keeps everything aligned true.

I'm not saying my method is the best and I can see it wouldn't be cost effective, because of the extra work and in all honesty, my brakes aren't as pretty as most of the commercial offerings.