Why 11 degree crown angle?

[thomae]

Recently I had too much time on my hands and I got to wondering... ::)

My perception is that "everyone" (admittedly, a sweeping generalization) seems to talk about 11o target crowns.
I understand that crowning the barrel protects the muzzle, but...
Is there a reason why 11o appears to be the de-facto standard?
Does it work better than 10o or 12o or some other angle??

I am not trying to pick a fight, just realized I was ignorant of the "why" and figured I'd ask.
Maybe I can learn something today.
Cheers,
Thomae

[earl39]

Good question Thomae. Here is what i found when looking for the same answer.

http://riflestocks.tripod.com/targetcrown.html

tells a little about crowning and gives a quick answer to your question.

[thomae]

[color=purple]earl39:
Thanks, good article.
Although it discusses the purpose of a crown:

The primary purpose of a firearm muzzle crown is to provide propellant gases a resistance free path away from all parts of the projectile as it exits the bore of the barrel. The secondary purpose is to protect the bore from damage caused by misuse. The third purpose is for good looks which is always achieved when the primary purpose is satisfied.

[color=purple][size=8pt]it does not answer the question as to why 11o is optimal.

It does state:

through experimentation and time eleven degrees is normally accepted as the optimum universal angle for this type of target crown.

[color=purple][size=8pt]I'd be interested in seeing that data. I can only presume that 11o somehow provides the optimal angle to allow the gasses to freely escape with minimum effect on bullet trajectory. (I am a little skeptical that this would actually hold true for both a 300 Win Mag and a .22LR, but on the other hand, I don't have the scientific background to know why this might not also be true. )

It also raises a question: The author recommends a 60o chamfer on the muzzle edge of the stepped barrel for the following reason:

The importance of this is to protect the bore edge from gas erosion and thereby ensure the bore exit remain smooth with no irregularities along its circumference.

[size=8pt]...and yet the author does not recommend a similar chamfer for the muzzle with the 11o target crown. I wonder why?

[teele1]

i know this does not answer the question you asked but is very interesting about the crown

http://www.precisionshooting.com/psm_2011_03_issue.pdf

jim

[darkker]

Taking a tip from Occam's razor(also written as Ockham's razor).. I would say that someone who was well regarded in the shooting sports, used 11 deg to good effect, or wrote about it being good. So naturally everyone followed suit.

Merely my $0.02

[frank1947]

glad you ask that question always wondered about all of that all of mine have the step down type target crown but my custom 30 br with a krieger barrel 1.250 ,25 inch and taper to 1 inch, built by Lester Bruno (Bruno shooter supply)has no degree at all just perfectly flat I am very careful about that not to bump it, not sure why he does it like that but I know he is a top smith and a long time benchrest shooter, and my 30 br is just unreal accurate for more then i am.

[Trent]

I think that it has been proven that it does not matter what the degree is, what matters is that it is cut perfectly to the axis of the bore. The gases need to leave evenly around the circumference of the bullet as it leaves the barrel.

[82boy]

It makes no diference at all, just most people use a 11 degree crown as an industry standard. I have Benchrest barrels that have a flat cut off, or a 0 degree crown, and they shoot no better or worse than my 11 degree crown barrels do.

[KTV]

Recently I had too much time on my hands and I got to wondering... ::)

My perception is that "everyone" (admittedly, a sweeping generalization) seems to talk about 11o target crowns.
I understand that crowning the barrel protects the muzzle, but...
Is there a reason why 11o appears to be the de-facto standard?
Does it work better than 10o or 12o or some other angle??

I am not trying to pick a fight, just realized I was ignorant of the "why" and figured I'd ask.
Maybe I can learn something today.
Cheers,
Thomae

What I was told is:

Many, many years ago, a team from the US Army decided to determine what
muzzle crown offered the best accuracy - so they took a rifle and many targets
and much ammo and then at a range they tested crown angles by firing groups
from the rifle and then cutting the crown angle back in 1 degree increments.

After examination of all the targets they found that best accuracy was obtained
when the crown was cut at 11 degrees. Since then, this belief has become an
generally accepted "norm".

FWIW

[Trent]

What I was told is:

Many, many years ago, a team from the US Army decided to determine what
muzzle crown offered the best accuracy - so they took a rifle and many targets
and much ammo and then at a range they tested crown angles by firing groups
from the rifle and then cutting the crown angle back in 1 degree increments.

After examination of all the targets they found that best accuracy was obtained
when the crown was cut at 11 degrees. Since then, this belief has become an
generally accepted "norm".

FWIW

If that is true then all they proved was what was the best crown for THAT particular rifle. You'd have to do that same test with a significant number of rifles of varying barrel types to prove it.