I just started shooting black powder last year and purchased a cabelas sportorized hawken 54 cal. I didn' t have much luck last year shooting the lead balls(blame everything but the shooter, right?) so I thought about trying the powerbelt bullets this year. Any one out there who has shot the powerbelt bullets from this type of gun I' d appreciate hearing from. I also had a problem with keeping the ramrod it it' s slot under the barrel. I glued a small piece of rubber block just above the forearm that worked pretty well but required a couple of glueings. I couldn' t believe the gun didn' t come with some kind of spring retainer to hold the rod in place. Anyone have a better fix I' d like to hear from.
I could hit a gallon jug at 50 yards free standing during practice with the lead balls but the shots would not be consistently in the middle of the jug. Ended up having to get my three deer with my bow. Doesn' t seem right does it.

I have the same rifle as you describe and mine came with a spring holder for the ram rod located between the forend cap and the first eye. Mine shoots the Lead balls alright of course i do not expect much of the rifle.

http://www.prbullet.com/
HERE A WEB PAGE TO CHECK OUT AND IF YOU SHOOT THEM A E MAIL THEY WILL ANS. WHAT WOULD BE THE BEST CHOICE OF BULLET.
I MYSELF SHOOT A 54 CAL T/C THUNDERHAWK THAT HAS A 1 IN 38 TWIST POWDER OF CHOICE IS PYRODEX SELECT
I ALSO SHOOT A 350 GRAIN POLY TIP SABOT THAT SHOOT CLOVER LEAF GROUPS EVEN OUT TO 100 YARDS

That twist will usually handle a short conical up to 350-385 grains. Some suggestions are
Buffalo Ballet 245s or 275s
Powerbelt 245s or 295s
CVA Deerslayer 300s
T/C Maxi Ball 320-350-370
Hornady Great Plains 385s
Some of these loads may require a wonder wad between powder & bullet

That twist also shoots tight-fitting short 44 cal sabot/bullets between 180-240 grains well. Some include

Hornady XTPs
Bear Claws
Partitions
Cheap Shots