My understanding is that there were two basic frames (of the hammerless guns), standard and featherweight. Featherweight frames were used on 12g, 16g, 20g and .410 guns and very likely the one 28g gun they allegedly built. I'm not sure which gauges the standard frame was used on other than the 12g and probably the 10g. I had a 16g LC built on a featherweight frame. While the featherweight frame is lighter than the standard frame, it doesn't necessarily make a feather weight gun.