The perfect crown?

[lazyeiger]

What does the perfect crown look like?

Are lands and grooves at a perfect 90 degrres to the bore with a sharp inside edge, or should the edge be relieved or maybe the lands should be chamfered? There are many combinations of these so I was wondering which works best and how to machine it?

Thanks Jon

 

[fdshuster]

Jon: I don't think anyone has ever proven one type of crown (contour) to be better than another. I've discussed this issue with both of my gunsmith's and they agree it's only a matter of concentricity: everything being square, parallel and true. I have custom barrels with several different types of crowns & have never been able to say one is better. Have never seen a scientific test done for comparison.

 

[clowdis]

I think that probably any crown design will work fine as long as you take the time to indicate the entire barrel straight in the lathe and indicate the groove diameter true at the muzzle. That way the crown is 90 degrees to the bore and exactly concentric to the groove diameter. All that being said, I like the 11 degree crown because I can see the "star" that forms on the end of the barrel from gases escaping around the base of the bullet and if the star is symmetrical then I believe the crown is good. A quirk I know, but it's my quirk

 

[jscandale]

You guys are all correct, in my opinion. Sometimes I cut a step crown and sometimes I do an 11 degree. I prefer the 11 degree. Some folks cut a square crown. I think that from a performance standpoint, there is no difference, but I always put a slight chamfer on just the lands as an added protection.
The way I have always understood the physics of a good crown depends on how concentrically the gas escapes from behind the bullet as the bullet leaves the barrel which is why special care is a must while indicating the center of the bore when cutting the crown with a single point cutter.

Works for me!
JS

 

[Larryh128]

I totally agree, can't see a big difference if done correctly. Lately I have been recessing a 11 degree crown just because it looks good & most guys don't have one ;D

 

[rvn1968]

These days I think that it is almost impossible to do a accurate comparison. We have so many options in internal barrel style , it would drive you crazy. 5R,polygon,gain twist,canted land,etc,etc,etc..... Personally,I think the only check a consumer can do is to chuck the barrel in a lathe or parallel v-blocks and look for uniformity.I just know that as I age, all of my rifles are more accurate than I.