Muzzle Crowns

[hanshi]

Not a very good pic but is the best photo I've been able to take of this muzzle crown.  I still use a short starter due to bad arthritic hands but must say this gun loads easily.  I remember seeing the great crowns on a former thread and was wondering if anyone has a comment on how this compares with their rifles.

[Daryl]

Looks pretty good- bit more angle beyond rifling depth than needed, but no problem with too much there. The corners of the lands, and at the bottom of the groove are generally what need polishing. The smoother that angle, the transition into the bottom of the groove and onto the top of the lands is the most important part of the crown in my experience.

This showed well yesterday when Taylor and I were trying different patches with the ITX hard balls is a slightly too-sharp crown. Even a .015" patch was cut on the corners of the lands.  This is a material you don't want touching the lands - ever.  Right now, the range is closed for some renovations, but when it gets open and the rain stops, I'll do some testing.

Note the corners where the metal angles out to the tops of the lands and bottoms of the grooves.  It should be smoothed, and this allows a tight patch and ball to swage easily together into the bore, instead of bunching up & pushing metal of the ball into an enlarged ridge and cutting the patch.

[hanshi]

Thanks, Daryl.  Is it safe to do this with my thumb and the black 400 - 600 grit paper?

[Daryl]

Here's one I just did yesterday, using Taylor's lathe and 320 grit.  When I started, it was a normal angled cutter crown as issued on almost all guns from their makers.  They can be done this way with just your thumb-end and .320, finishing with something finer, or done more quickly with a latche, of course. Keep rotating the barrel as you progress.  The difference in starting the ball and subsequent loading is incredible, compared to a sharper crown.  This is not coning per-se, as only the very end of the barrel is shaped,radiused, smoothed and polished, not the interior in depth, like in a cone.
The first one I posted is my .69, done entirely with emery or paper and my thumb.  I load a .684" pure lead ball in it with a .030" denim patch. This combination is .030" larger than the groove diameter, for .015" compression per side. It provides the load that shoots into 1 1/2MOA at 200 yards, off teh bags, of course, with the rifle's Express sights.



Here's a closeup, albeit a bit fuzzy, of the same .50 cal barrel.