A nicely radiused and polished crown will work on all rifles, no matter the calibre. A search with "muzzzle crowns" in the title should bring up some pictures.
Rayle's and eveyone elses have sharp edges that I feel need to be broken. This can easily be done with a piece of 320 emery cloth, pressed into the crown and rotated, or wrapped around a tapered instrument like a case mouth chamfer tool used on reloading benches around the world. for a .25, a newly sharpened pencil might work as the guide for wrapping the cloth around. Rotate the cloth and trun the barrel 180 degrees a few times while 'polishing' the crown.
If you want to shoot loads that require frequent cleaning (weak, wimpy, limp qristed, thin patch loads), you probably don't have to change the crown. IMHO, of course.
