I'd go to the range and shoot 3 shot groups starting at 60gr. Go up 5 grains per string up to 100 grs. Take your time and clean the bore after every shot. Shoot each string at a clean target or measure each 3 shot group and note it. Pick the tightest group and stay with that.
The fox river .54 was sold by cabelas in the late 90s early 2000's time frame. I only know cause my mom bought one for my dad, tho it has a wood stock IIRC.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |