.410s pose their own unique difficulties due to the vast difference in ratios of muzzle diameter to breech diameter, I think.
As one time, I was going to use one to make a 'cape' gun for deer and moose, by chopping off the barrels at 24" from the normal 26 or 28" (reoving the chokes and thickening up the muzzles, then rifling one of them using a .45 cal rifle barrel (18" twist as a guide), then 'jug' choke the other for shot. The 18" would easily shoot a 350 to 400gr. bullet with up to 90gr. black powder, and, of course, 2 1/2" shot loads in smokeless for the shot barrel for shooting grouse.