View Full Version : Countersink for barrel crowning?

June 20, 2002, 17:46
Being a machinist and having lots of countersinks laying around. Would I be able to use one of these to crown my barrel? Actually, I know I could but what does the angle have to do with accuracy?
I guess if I don't have the right one I will have to use the lathe. Bummer!

Upside Down @ 100 MPH
June 20, 2002, 18:32
The angle is not important, it's the concentricity of the cut. Also, a countersink would probably leave a burr at the crown/bore junction. If you have a lathe, use that.

June 21, 2002, 15:29
If you have experience as a machinist, it seems like a reasonable project. If you burr it, you can fire a magazine through the barrel, then use lapping compound or sandpaper to eliminate the residual burr. Unless the muzzle is buried under a big ol' muzzle-thingy, you should be able to give the crown a close inspection with a magnifying glass.

The commercial crown-cutter tool is nothing more than a countersink is it?

If you mess it up real bad, you can just cut off the buggered area.

Be bold!

June 21, 2002, 15:44
Thanks. I was more worried about the angle. Actually, I already had it in my lathe when I shortened and rethreaded the barrel. I just stuck a countersink in the chuck and went at the muzzle with it before I took it out of the lathe. I don't see any burs so I think I will be okay.
What really surprized me was when I screwed on my muzzle thingy. Without even trying, the darn thing timed perfectly!:cool: Just don't ask me to do it again!

June 21, 2002, 16:25
Use your lathe. I set mine up in a steady rest and did it in about 20-minutes.

June 21, 2002, 22:47
A good way to check for burrs,is to use a Q-tip.Loosen the wrap of the cotton and insert into bore,pull it out with light pessure on the bore.Go all the way around the barrel.If there are any burrs you will see strands of cotton.Light polishing or lapping should take care of it.

Upside Down @ 100 MPH
June 22, 2002, 00:18
Originally posted by gary.jeter

The commercial crown-cutter tool is nothing more than a countersink is it?

True, but the thing about countersinks is that they really aren't sharp enough for the job. A new or freshly sharpened carbide tool should be used for the job. The cut should be from the bore outwards and the material should come off in a string like shaving. If it's done like this it doesn't need lapping. But the piloted countersinks are the next best thing. Most FAL's and the ammunition fed them aren't accurate enough to realize the difference between the different types of crowning but we still must do what we can.

June 22, 2002, 00:39
With the barrel in the steady rest, I set the compound at 11 degrees and cut from the bore out. The G1 barrel I cut off and crowned machined very smoothly and required only a touch with 600 grit to complete.