From the Gun Digest Black Powder Loading Manual
Lyman Plains Pistol
Caliber: 54
Rate of twist: 1:8"
Depth of groove: .0095"
Projectile: .530" 225 gr. Denver Bullet Co. round ball
Powder: GOI
patch: .013" pure linen
Luge: RIG
Ignition: CCI No. 11
Powder Measure: Uncle Mike 120
Vol wt mv me vel energy (50 yds)
30 FFFg 30.9 860 370 753 283
40 FFFg 41.2 952 453 819 335
30 FFg 29.6 743 258 650 211
40 FFg 39.5 856 366 749 280
50 FFg 49.5 926 429 803 322
Sorry, but there's no listing for the 50 caliber Lyman GP pistol. However, there are 50 cals listed.
Kennedy English Dueler (9" 1:29" twist, .010" groove, .490 ball & .012" patch)
30 FFFg 31.1 776 237 677 180
30 p 22.3 712 119 622 152 Pyrodex
Kennedy Kentucky Pistol (9" 1:29" twist, .010" groove, .490 ball & .012" patch)
30 FFFg 31.1 781 240 683 183
30 P 22.1 751 222 655 169 Pyrodex