Cutting a barrel crown.

I machined a 10/22 blue barrel for a two point mounted suppressor(form1). The last two inches of the barrel werre turned down to .485", with 9/16-18 threads on the rear part of the machined portion. I finished by cutting an 11 degree crown onto the muzzle. This is the first crown I have cut. I had slight chattering problems. The cutting tool was mounted in a tailpiece chuck and the barrel turned at 180 rpm (my slowest ), while using a steady rest.

My problem is that accuracy, while never great (3/4" at 25 yards) has degraded by about 25%. I think it is the crown I put on causing this. Do I need to "shoot in" the new crown? Does a cutting tool tend to push metal up and into the bore? Is there a way to stone the muzzle to prevent this? Would a flat crown followed by some stoning work better even if it leaves the edge of the rifling exposed? Thanks.

Ranb

Should not need to shoot in any crown. Yes a cutting tool can leve burs in the barrel, have you cleaned it yet? if so did you notice any lint from the patch at the crown? A sure sine of a bad bur. You can try a brass ball around 5/16 inch with some laping compound, 320 grit, and lape the crown, or recut it. As for shape of crowns, it makes no def. as long as there square to the bore and bur free.

[This message has been edited by Kurt Westfall (edited 12-28-2003).]

I indicate the bore in just like I was chambering. As Kurt says, The angle is not important. I use a cemented carbide tool ground by Jackie Schmidt, a long time machinest and benchrest shooter. It is a very sharp tool with a lot of clearence and relief. It also has a chip breaker ground on it to make it sharper, not for chip breaking. This tool is used for nothing else and I don't let any body else use it. Butch Thebarrelman

Ranb I will add that these darn rimfires are touchy about were you cut the barrel, what won't shoot today may come alive with .500 cut off the end. Unlike a centerfire, were you work up a load for best accuracy, on a rimfire you have to tune the rifle to the ammo.