Crowning a barrel

[scrat]

sam steele posted this photo of the crown of a 2nd Generation Walker revolver:

File marks going in same direction with just the rough edges filed down is not a proper crown

 

[scrat]

This is an EXCELLENT VIDEO ON A PROPER CROWN.

http://www.youtube.com/watch?v=-Xpzv1Spsnk

 

[Strykervet]

The last inch or so of a barrel, and in particular, the last part the bullet touches, the crown, is the most important place on the barrel for accuracy. Any rifle, any calibre, any propellant. While important for ball, I'd imagine it is even more important for mini ball and for square or flat base bullets.

If the crown isn't square, and I use "square" as a relative mathematical term, then the bullet will in theory be touching one part of the barrel and not another, at the moment the bullet leaves the barrel.

I feel a proper crown is crucial. If valve grinding compound an a good spherical end are all you have, so be it, but there are machine tools that work quite well for this, and some that can even be used by hand. I cut and crowned a .303 barrel, when I was done, you'd think it was made that way. And I fired it before and after --the crown certainly made a difference. My friend was a machinist and happened to have the tool, so I crowned it by hand on a road trip to Montgomery when I was 18. Not the best way to do it, but hey, I was a redneck kid.

I may make it sound like the crown does more than it really does, but it is important. You can get by with no crown, provided the muzzle is cleanly deburred and it is never ever damaged (like with the fellow above and his false muzzle attachment). The purpose of the crown is really to protect the rifling in that last mm of barrel and to even up any part of the cut that wasn't square to begin with. If you have another means to accomplish this, by all means...

 

[scrat]

+1 what he said

 

[arcticap]

Here's a diagram concerning crowns:

http://riflestocks.tripod.com/targetcrown.html

 

[gifford]

This has been an interesting thread, especially the discussion of the false muzzle pin holes.

Articap - great link on the target barrel crown operation. Thanks.

 

[BCRider]

I use a hardened ball bearing with a welding rod attached to crown barrels. The rod is chucked in the drill, the bearing is coated with valve grinding compound, and away we go.

Never crowned a BP barrel.. I have some modern rifles. I was taught to use a hardened carriage bolt in my drill with valve grinding compound.

Sorry, but you two are doing it wrong. For lapping compounds to work they need to embed into a softer metal and then they'll act like sandpaper on the harder metal. To use such tricks to crown a barrel you're far better off to find a brass round head screw to use as your lapping tool. The metal of the lap itself MUST be softer than the material being lapped. And since most barrels are not all that hard you need a very mild steel or brass or aluminium for the actual lapping tool. By using hardened steel such as the ball bearing or hard screw all you did was jam the grit into the barrel and wear out your ball bearing and screw.

It is not absolutely necessary. A flat crown can work very well. A rounded crown is less prone to damage. A lot of octagon revolver barrels are flat crowned. The important thing is to get the end of the barrel square with the bore and burr free.

Yep, nothing wrong with a good square cut end. But as noted they are that much easier to damage.

Another key point is that the end MUST be square to the bore axis before any sort of crowning step is done unless you're using a special crowning tool setup. This especially applies to using a brass scew to lap a crown chamfer. If the end face is not square to the bore axis lapping in a chamfer won't correct this error. And for most of us getting the end face truly square to the bore axis means using a metal lathe. "Close enough" isn't close enough when it comes to this sort of thing.

 

[burnse]

Would the 11 degree crown be appropriate for my revolver? I try to be careful, but I'd find away to screw up a squared end.

 

[Wolfebyte]

Quote:
Originally Posted by alsagr
I use a hardened ball bearing with a welding rod attached to crown barrels. The rod is chucked in the drill, the bearing is coated with valve grinding compound, and away we go.
Quote:
Originally Posted by Wolfebyte
Never crowned a BP barrel.. I have some modern rifles. I was taught to use a hardened carriage bolt in my drill with valve grinding compound.
Sorry, but you two are doing it wrong. For lapping compounds to work they need to embed into a softer metal and then they'll act like sandpaper on the harder metal. To use such tricks to crown a barrel you're far better off to find a brass round head screw to use as your lapping tool. The metal of the lap itself MUST be softer than the material being lapped. And since most barrels are not all that hard you need a very mild steel or brass or aluminium for the actual lapping tool. By using hardened steel such as the ball bearing or hard screw all you did was jam the grit into the barrel and wear out your ball bearing and screw.


Quote:
Originally Posted by junkman_01
It is not absolutely necessary. A flat crown can work very well. A rounded crown is less prone to damage. A lot of octagon revolver barrels are flat crowned. The important thing is to get the end of the barrel square with the bore and burr free.
Yep, nothing wrong with a good square cut end. But as noted they are that much easier to damage.

Another key point is that the end MUST be square to the bore axis before any sort of crowning step is done unless you're using a special crowning tool setup. This especially applies to using a brass scew to lap a crown chamfer. If the end face is not square to the bore axis lapping in a chamfer won't correct this error. And for most of us getting the end face truly square to the bore axis means using a metal lathe. "Close enough" isn't close enough when it comes to this sort of thing.

Thanks for that.. I've not done it in many years.. I do know we used carriage bolts ... maybe they weren't hardened?? 'course that was several years ago

 

[SAA]

Would the 11 degree crown be appropriate for my revolver? I try to be careful, but I'd find away to screw up a squared end.

The 11-degree crown was designed primarily for optimal angle to the boat-tail on boat-tailed bullets.

 

[burnse]

Maybe a 40 or 45 degree, then?

 

[SAA]

That's too extreme. You may get some of the muzzle blast deflected back at the bullet, upsetting it. 11-degree may work fine, I don't know, but any standard crown that is true and deburs the bore/muzzle edge should do the trick on a handgun.

 

[scrat]

Stick with 11 degree.....

Picture this in your head slow motion.

A bullet traveling down the barrel being pushed at a high rate of speed with a huge fire force behind it. As it reaches the end of the barrel. The barrel is not square the bottom sticks out just a hair. maybe even 05 thousands of an inch the filed crowning did not fix the issue either as it leaves the bullet will rise as the force and fire will still be hitting the bottom.

Now picture that on the side or on top. Bottom line the end of the barrel needs to be true and the degree of crown needs to be true so that the bullet will fly true and straight and will not be forced to go off course

black powder or not does not make a lick of difference. you take a 30-06 match grade barrel shooting competition 400 yards a barrel that is not crowned right will suffer and will loose.

Take a black powder Sharps 45-90 using for same competition shooting 400 yards. If the barrel is not crowned right you are going to suffer. Now take a cap and ball revolver shooting at a piece of paper or steel at 20 feet. You may think your steel rod back yard bubba crowning is the best thing since sliced bread. However you are only shooting at 20 feet at a piece of steel 1 foot wide. WHO CARES nice crown