I've been wanting to do that build myself but don't have the tools or donor gun-what .410 are you planning to use? My idea keeps going back to the EAA doubles that were common a few years ago. .22LR or .22 magnum doesn't need any more strength than .410, and the EAA gun has the contours I want. Might get a couple blanks or 12 gauge inserts and have a friend turn them down to fit the .410 bores on his lathe. Another idea I have had for years is this-anyone know if it would be legal to permanently insert the .22 barrels into the donor barrels(blind pin and silver solder), and cut them to 16"? If permanent, by common sense thinking the gun's not really a shotgun anymore, but we all know the BATF doesn't always follow common sense reasoning.