This rifle was made by lining the bbls of a 20 gauge SxS so the .405 allowed more meat in the chamber. This made for a very slim rifle and only 9 Lbs.

Regarding the 400 grain bullets. I think they will out perform the 300 any day at short range (50-100 yards). The sectional density is a high .338 and I can shoot the great Woodleigh solids.