I use brass 24 Gauge shot gun shells to make 577/450 Martini cases. Some also use the 24 gauge brass cases to make 577 Snider. Those folks also us plastic 24 gauge cases to make Snider cases. Some Sniders have misshapen chambers and the flexibility of the plastic allow the case to fit odd shaped chambers. I make 450 Westley Richards Musket No. 2 cases from the brass 32 Gauge shotgun cases, although I prefer using 50/90 Sharps cases. The Sharps cases are solid head, whereas the brass shot gun cases are semi balloon head and have a tapered shotgun rim.