You can do a lot better than that cartridge. The cartridge is tricky to load for and not very efficient. It is a poor choice for making express cartridge...I know I shoot it also.

(Just finished resizing 200 Martini cases getting ready for eh Victorian Rifleman shoot in Bowden, the 25th and 26th.)

Have you considered a 450 Musket number 2 sometimes incorrectly refered to as a 500/450 it is a much more efficient and direct competitior of the 577/450.