The circles seem to be more of a guide for the punched dots/small stars, so the maker can keep the punch marks "reasonably" spaced and organized. Several old "tales" float around about why the marks were used; one such story in Kentucky lore [from a county history, but NOT from the gunsmith himself] is that they identified a gunmaker's work. Perhaps that was a "little bit" true in a local market when a gunsmith did not sign a particular rifle, and only one or two gunsmiths were in the area, but muzzle designs are so similar and common it doesn't hold up well on a larger scale.
If we are going to have fun coming up with modern interpretations for why the old muzzle designs appear, one possibility is protecting the muzzle's integrity. It might be easier to detect the extent of damage on a dropped or "dinged" muzzle when it was decorated and the lines/dots got moved "out of kilter" a little, rather than looking at an unmarked muzzle surface. And then there could be the possibility that stamping the muzzle with evenly [well, almost] spaced rings of punch marks around the muzzle might slightly work-harden and stabilized the soft iron around the bore to better protect its integrity and accuracy. Or maybe it's just simple decoration that was easy to do and expected by the buyer.
Shelby Gallien
