Muzzle crown angles?

[MagnumManiac]

Hey all,
I am finishing up my barrel on my custom switch barrel, it is the 29" 6.5 1:8" chambered in 264WM. The lapping job on this is excellent, I don't have to do anything!

I just finished chambering, threading & cutting recesses for bolt noses etc, now I am at the point of doing the crown, what crown angle works best for LR, is it 11,13 or something else?

Cheers.

 

[Canadian Bushman]

If its perpendicular to the bore and the bore/crown intersection is burr free, it makes no difference.

In my experiments shallower than 11 deg. i get a drastic reduction in soot markings on the crown. Whatever that means.

I have come to put plain 11 deg. crowns on my rifles just to protect the bore's edge a bit and for ease of cleaning.

 

[nksmfamjp]

For a field rifle, is there some value in recessing that like 0.03-0.05" first?

 

[Rhovee]

Leave it flat if it's got a break

 

[Canadian Bushman]

Leave it flat if it's got a break

Why is that?

 

[Rhovee]

It can't get damaged.

 

[BallisticsGuy]

I've been setting my crown angles based on the boat tail angle of the projectile for a few years. A gun I'll shoot just flat base bullets from gets a 4deg crown that's recessed .060, a 7deg boat tail gets a 11deg crown, a 9deg boat tail gets a 13 deg crown. It started out as an experiment and still is one but data gathering is only as fast as I go through barrels.

 

[MagnumManiac]

Thanks guys,
Looks like the 11 degree is what I'll go with.
Muzzle is .900", so I'll go .150" flat then 11 degrees from there in to the muzzle.
Still don't know if I'll break the edge with a 45 degree cutter just to clean up the rifling?
See how it all goes, can't shoot until September 14.

Cheers.

 

[Canadian Bushman]

I again see no accuracy difference between a chamfer/un-chamfered crown. However i do prefer to pull bore the chamfer with a small boring bar over doing it with a multi flute cutter.

Its less tool pressure, less chance of burrs and raised edges, and also less chances of the flutes timing up with the rifling resulting in chatter.

Just my preference

 

[Pat Byrne]

Absolutely do it with a single point tool.. CB has it right, angle is pretty much irrelevant..
Make sure to indicate the bore in perfectly if doing anything other than a 90' crown, even then indicate the bore.. single point tool, positive rake, sharp.. Pull the tool from the bore out.

 

[D-mon]

I do 30degrees on mine, ( nothing wrong with 11 or flat also), with a very small polishing with 800 grit paper to finish, it gets rid of any potential burr and no need for a 45 degree chamfer then. Works with brakes and silencers ,no problem either.

 

[MagnumManiac]

Will be using a boring bar, didn't mean to imply I was using a multi cutting head tool.
I have left them square in the past, but found it took a lot longer to smooth out over a slight counterbore.

Cheers.

 

[aushunter1]

It can't get damaged.

So do crowns just protect the rifling or is there some affect they impart on accuracy?

Im just curious as I have some rifles with very different crowns & wondering why you would use 1 over the other??

Similar to this-

 

[Rhovee]

I am not a gun smith. But i don't think it matters on angle. The 11 degree came from the boat tail bullet design. Most of mine are flat with muzzle breaks. Bench gun looks similar to yours. I believe the main benefit is to protect the rifling.