Crowning

[hemiford]

It seems to me that the critical feature of a good crown is that
it must be radially symetric. The particular shape or angle of the crown
may (probably) has a minor effect on MV, but I can't begin to guess
more on that.

 

[Boe]

Hammer111,
No, I haven't worked on the Bmag. I primarily build centerfire rifles. When machining a crown the same principles apply regardless if it's a rimfire or centerfire.

Richard Hilts
Hilts Accuracy Custom Rifles

 

[J E Custom]

It seems to me that the critical feature of a good crown is that
it must be radially symetric. The particular shape or angle of the crown
may (probably) has a minor effect on MV, but I can't begin to guess
more on that.

Barrel length is measured from the bolt face to the crown bore (The shape has nothing to do with the bore length or the velocity) the overall barrel length can vary based on the type of crown used, but the bore length is what effects the velocity.

The shape/style of crown can have an effect on longevity/crown life based on use to some extent but mostly is a personal preference.

I prefer the 11o crown because it makes the exit edge of the crown 101o instead of 90o making it last longer and maintain its function longer.

Most bench rest shooters prefer the 11o crown, and some claim it improves accuracy because it approximates the angle that the gases exit, making it a more stable exit of the gasses. I can nether agree or disagree with this theory. Some like the 90o crown because they say it gives the gas a clean unobstructed exit from the barrel.

A good crown should only effect accuracy.

J E CUSTOM

 

[Edd]

I like a deep 30° crown and then a very narrow 60° cut at the edge of the bore. That helps to keep me from bumping it against stuff.