Originally Posted by Susquatch
Someplace over 30 years ago, I recall reading that the military did exhaustive testing which showed that 11 degrees was the optimum crown angle for best accuracy. Not by a huge margin, but still significant enough to be the recommended angle of choice.
However, I also recall that this assumed a perfectly perpendicular cut.
The theory behind the 11degree crown was based on high speed photography testing done by
It appeared that the gas escaped at close to 11o from a squared of crown and that more than
11 degrees of crown caused the gas to contact the surface of the crown and possibly having an
effect on the bullet.
So they theorized that any thing from 0 degrees to 11 degrees had no contact with the surface
of the crown preventing any effect of the shock wave or gas on the bullet.
After some firing some crowns have Smoke trails that match the rifling from contact of the
escaping gas and 0 to 11 degree crowns have little or none.
I am not sure that the High pressure rounds perform the same as the test done by the military
but a good clean exit of the gasses does make a difference.
The gas and unburnt powder can and will erode the crown over time and it needs to be re cut
when this happens.
The 11 degree crown has a thicker edge than a square crown (90 Degrees compared to 101
degrees of the 11o crown)from the bore and should last a little longer. Does it? I cant prove
it, so the choice is from 0 to 11 degrees.
This is all theory like lots of other things in ballistics, and the reason that there is so many opinions
I like the looks and it seems to work good so I use 11 degree crowns.
But I do think that any well cut crown 0 to 45 degrees will work if it is true and clean to the bore.
If you look at some of the factory crowns they are not concentric to the bore and are there to
aid in cleaning from the muzzle without tearing the patches.
Note: never clean a barrel from the muzzle end if possible.
J E CUSTOM