In my Taylors 56-50, I am using Starline brass, untrimmed, and the Rapine 512-350-T bullet, 358+/- grains cast from straight wheelweights. The overall cartridge length is 1.510" - 1.515". This feeds through the magazine without any problems. A couple of days ago I shot 5 magazines full, one right after the other, without a hitch. This round is loaded with 29.0 grains of GOEX FFg powder and Winchester Large rifle primers, no wad over the powder and the bullet lubed with SPG lube and sized to 0.512". This gives about 0.020" compression and the bullet is crimped in place. At 100 yards this cosistently hit the gong that I was shooting at offhand. I haven't had to chance to check it from a rest yet. That's next.
Good luck and good shooting.
Hell-Er High Water