View Full Version : 45deg vs 11deg barrel crown... what's the diff? pros and cons?

02-14-2007, 7:23 AM
While trying to decide the exact spec of ordering a custom barrel for a SPR-clone build, I came upon the question of whether to use a 45deg crown or a 11deg crown, can someone help?

The military SPRs seems to be with 45deg crowns, while the 11deg crowns should be "more accurate".... so WHY do the military chooses to use 45deg crowns? Does it have anything to do with durability? Does it have anything to do with the OPS-INC brake (or that military rifle generally has some sort of brake or suppressor mounted?)


02-14-2007, 7:29 AM
The type of crown does not really determine accuracy. It is important that it is uniform and done properly.

Most gunsmiths who use an 11 degree crown usually put a 60 degree chamfer for an extra degree of protection for the lands.

I don't think it really matters since you'll be putting a muzzle brake which already offers a certain degree of protection for the crown.

02-14-2007, 7:40 AM
The 45 degree is more durable (it'll take more effort to damage it).

02-14-2007, 7:47 AM
The 45 degree is more durable (it'll take more effort to damage it).

I have to ask, How?

02-14-2007, 7:54 AM
The only difference that I can figure is that with a 45 degree crown the actual edge of the barrel/lands would be deeper than in an 11 degree crown.

If you hit the muzzle hard enough to dent/cut the steel it would have to be about 1/4" deep before it hit the actual crown on a 45 degree job but the 11 degree crown would have thicker metal at the outer edges (because the angle of the barrel cut is shallower) so it should harder to damage all the way to the actual crown.

02-14-2007, 11:11 AM
On a 45 crown, the angle at the termination of the rifling is 135

On an 11 crown, that angle is 101

The more obtuse angle will support more force before yielding. i.e. If you take two axes and sharpen them at different angles, the wider angle one will stay sharper, longer and will get fewer dings.

On a rifle that you clean from the front, it's a big deal. Not so much on one that you clean from the breech end.