Ed - HB bullets are much more difficult to cast perfectly, that is, without shrink voids (cavities) inside the HB cavity. If you are new to casting, I suggest you slug the bore and purchase the appropriately sized mould with a solid base. Most .45's are .457" to .458" groove to groove, but slugging will provide you with the exact specs on your rifle's tubes.

Small grease grooves will produce a LOT of anxiety when shooting REAL black powder. Lube balls and special wads are usually necessary. The reason for capitals REAL, is that some people call the replica's, black powder - they are not.

BuffaloArms has REAL black powder bullet moulds, meaning moulds designed for shooting REAL black power. These have large, square bottomed grease grooves.