All barrels have crowns. As soon as a barrel is made, it has a crown. When you hack saw off the end of the barrel, you have just created a new crown, not a very good one, but you have one. I found this description on the 'net.
Crown
The crown is simply the circular edge where the rifling ends at the business end, or muzzle of the barrel. This area is often damaged by improper cleaning, that is, cleaning from the muzzle end and/or scraping it with the cleaning rod. If a jointed cleaning rod is used there may be burrs or nicks where the joints slammed into the crown.
A good, crisp crown is essential for accuracy. If the rifling ends on one side before the other, the bullet will be tipped as it leaves the barrel. It will take some time to settle down in flight, during which it will diverge (in random directions) from the ideal flight path.
How good (square) the crown is to the bore, makes a difference in accuracy. Some swear by an 11 degree crown. Some really like a stepped crown similar to the H&R type crowns. I have a very accurate barrel that was basically flat with a chamfer on the out side of the barrel and in the bore. The shape of the crown in a lot of cases is to protect the area where the bore ends. No matter what type of crown you have, it must be square with the bore. I do not think it really matters a whole lot the shape of the crown as long as it is crisp and square. I think some prefer the target style crowns because they are easier to keep square and crisp when they cut them. The shape of the crown some times makes a difference what type of bullet it likes best. Some seem to like a flat base bullet better and some seem to prefer a boat tail type bullet.
