At .585" groove depth, you'll need a dedicated mould of course.

As far as holding enough grease - if using REAL BP lube (BP Gold or SPG) as I did, the lubrication I applied was sufficient for repeated shots and group shooting with no loss of accuracy. Whenever shooting a smokepole (or BP ctg. gun), I loath having to wipe the bore until I am finished shooting the group or with patched round ball, shooting for the day.

Only the outside grease grooves were lubed. Good PROPER lube makes a difference and is fully capable of holding accuracy for a 5 shot group + a fouler if need be.

I'm sure you'll get it sorted out.