Competition Crown Configurations?

[Papa Charlie]

Looking into different crown configurations for my F-Class rifle (.308 Win). I shoot Berger 185gr Jugs, 2705 fps.

I was wondering if anyone has done any testing on the angle of the crown cut (7-13 degrees) and how it might relate to the consistency in performance with different bullets (configuration, weight, etc).

Probably going too far down in the weeds, but I am sure that someone has as much if not more OCD than I do and has looked at this.

Wish my lathe was out of storage and set up so I could do my own testing, but that is at least 6-9 months away.

 

[LVLAaron]

Flat

 

[jackieschmidt]

It has been tried and discussed many times.
A 90 degree burr free crown is as good as it gets.

 

[kendog]

...Probably going too far down in the weeds, but I am sure that someone has as much if not more OCD than I do and has looked at this....

Probably so. Concentric and square are the most important features of a crown.
When you are done here, you might want to go over to KTMTalk and inquire which oil is the best. Tell them why Yamalube is far superior to all the rest, then hold on to your hat!!

 

[Papa Charlie]

Thanks, much appreciate the help.

 

[Alex Wheeler]

If you take the same care to dial the crown as the throat I see no difference. A small chamfer is more durable. I will usually chamfer a hunting rifle or something that lasts a long time like a 30 br. Stuff that we pull off fast like the 6mm BR stuff I cut flat. I can site a bunch of BR records with flat and chamfers.

 

[Papa Charlie]

If you take the same care to dial the crown as the throat I see no difference. A small chamfer is more durable. I will usually chamfer a hunting rifle or something that lasts a long time like a 30 br. Stuff that we pull off fast like the 6mm BR stuff I cut flat. I can site a bunch of BR records with flat and chamfers.

Thanks Alex, I have been getting ~3000-4000 rounds per barrel. So will go with a chamfered crown.

I assume that the degree has little impact, so may settle for the 11degree. I was however curious why some have chosen a little as 7 and as much as 13 degrees. Probably like everything else in this sport, "because".

 

[Alex Wheeler]

So much of the testing you hear about is very flawed. Now a test is always better than opinion but to really test something like this would take quite the effort to know 100% the difference between a few degrees in crown angle. Lots of bullets, barrels, time, ext. No one is going to do it because theres far more important things to test that will make a difference. My opinion on this comes from anecdotal evidence. What I do know is if its done right it wont stop you from breaking the smallest group agg records in LR BR either way. You should be confident that no matter what angle you use is will be right. If I had to do a barrel between centers Id probably lean towards a flat crown.

 

[jackieschmidt]

I was however curious why some have chosen a little as 7 and as much as 13 degrees. Probably like everything else in this sport, "because".

“Because” of the Internet.

”Hey, did you hear that the winner of the Super Duper Shoot uses this kind of crown”?
Great. So does the guy that came in 57th.

 

[X Count]

As others have said. Doesn't seem to make much difference if done correctly

It's interesting to look up some high speed videos of bullets exiting muzzles with various crowns and bullet base types.

Some things you see. The steeper the crown the more gas is pushed forward. With boat tail bullets the gas starts "jetting" out around the perimeter of the bullet before it leaves the muzzle and goes well forward of the bullet. With flat base bullets more gas seems to go out at 90 to the bullet and not as much gas goes ahead of the bullet. These things might be the reason flat crowns and flat base bullets are good.

 

[kendog]

“Because” of the Internet.

”Hey, did you hear that the winner of the Super Duper Shoot uses this kind of crown”?
Great. So does the guy that came in 57th.

He wore a pink tutu also. Next match... guess what...?

 

[Jud96]

I like a flat recessed crown just because it looks good to me lol

 

[jackieschmidt]

I like a flat recessed crown just because it looks good to me lol

View attachment 1597449

^^^^^^^Me too.

 

[WSnyder]

^^^^^^^Me too.

Same

 

[Jonnyofalltrades]

I like a flat recessed crown just because it looks good to me lol

View attachment 1597449

Yep.

 

[Greg@wfcustom]

Yep!
Flat for .100 out from bore, then taper out from there at what the compound is set to. Usually go .025 deep for no other reason than it looked right.
YMMV
G

 

[FireMedic]

If you take the same care to dial the crown as the throat I see no difference. A small chamfer is more durable. I will usually chamfer a hunting rifle or something that lasts a long time like a 30 br. Stuff that we pull off fast like the 6mm BR stuff I cut flat. I can site a bunch of BR records with flat and chamfers.

30 deg chamfer? Or do you think it matters? I typically do a 30deg because that’s where the compound is already set

 

[LVLAaron]

30 deg chamfer? Or do you think it matters? I typically do a 30deg because that’s where the compound is already set

Same here. I cut maybe 6 thou. Just enough to break the edge

 

[Alex Wheeler]

30 deg chamfer? Or do you think it matters? I typically do a 30deg because that’s where the compound is already set

Doesnt matter