bls,
Ok, I'll offer my thoughts. I've hunted birds and shot clays with a variety of sxs's, both sidelocks and boxlocks. I had been looking for my perfect grouse and woodcock gun (don't we all?) and was looking for a light 12 ga. choked more open than my usual IC/Mod ones. In my search I found a 12 ga, 26" barreled sxs weighing 5 lbs. 12 oz. and choked .003/.011. It happened to be a Churchill boxlock that was a precursor to the Hercules model. I prefer the boxlock to the sidelock for light weight and smoother edges not to mention cost.
I won't admit it to my wife, but I believe I've found that perfect grouse and woodcock gun. If you look for a Regal or similar model Churchill, you should come in at a reasonable cost. I find that neutral balance is the key, as well as forming a muscle memory to effectively use a light and balanced gun.
Good luck in your search,
Karl
