Considering joining the club...

[old tanker]

I have a Marrtini and had good luck using the steel adapter. Standard .45 Colt bullets are considerably undersize. Factory .45 Colt ammunition went bang reliably but the group at 25 yards you could just about cover with a poncho. Handloading, I found that reasonably good plinking accuracy was possible using hollow base bullets intended for .455 Webley. Cast from pure lead using an RCBS Mold 45-265-RN-HB and loaded over 5.5 grains of Trail Boss thy will do "minute of coffee can" at 100 meters. They work well with black powder too, but you greatly increase the risk of getting the adapter stuck if you don't keep things clean.

Lee makes a .454 Minie Ball Mould that some people say works well, the hollow base expanding to fit a Martini bore, but that I have not tried.