Considering joining the club...

[Patrick Chadwick]

Factory .45 Colt ammunition went bang reliably but the group at 25 yards you could just about cover with a poncho.

- No surprise. The factory loaded 45s would probably have a lead alloy bullet with approx. BH15 or more and would hardly upset into the bore.
Since the groove diameter of a .577-450 barrel at the breech end is something in the range .470"-.480" they are just going to rattle down the bore and not take the rifling properly.

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.

Once again, no surprise. The soft lead bullets with a hollow base can expand to fill the bore much better. But the bullets are still too short to provide the kind of accuracy one expects from a rifle.

As you have already been bitten by the M-H bug, I strongly recommend that you search around here

Martini-Henry Forum - British Militaria Forums

where you will find more information on shooting M-H´s than anywhere else.