Did a full rebuild/customization on my Pedersoli Frontier recently and finished it off by dimpling the muzzle. Really easy to do, just stay away from the outer edge and bore/crown because it CAN/WILL displace a lot of metal if struck really hard or very close to the edge. The trick for me was just (light, repeated) taps with a hammer, then file smooth, done.
Here’s a pic of the set up. Wrap tap evenly around your ram rod so it fits snug in the bore then shim and tape a center punch to it in the desired position. Simply strike it once and rotate, repeat, repeat, repeat until satisfied with the depth, diameter of the dimples. Be sure to strike the punch only once then rotate. Multiple strikes can cause the punch to jump and make an oblong dimple or double dimple. Then file the raised ridges smooth if desired. Be sure to post pics!
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