This is some data from Mike Venturino.
.45-60 WCF / .45-60 Winchester (Venturino Lever Gun Data)
Warning! Notes: test gun: Winchester Model 1876 28"; Federal Brass shortened to 1.89 inches; Federal 215 Magnum Large Rifle Primers; group - two 5 shot groups @ 100 yds. ("Shooting Lever Guns of the Old West")
Be Alert: Publisher cannot be responsible for errors in published load data.
Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS)
324 RCBS #45-300FN Goex FFg 60.0 1,310
Remarks: groups: 3.38 & 5.25
324 RCBS #45-300FN Goex Cartridge 62.0 1,328
Remarks: groups: 2.75 & 3.63
324 RCBS #45-300FN Hodgdon Pyrodex Select 42.0 1,351
Remarks: groups: 4.75 & 4.50
From Handloader #44.
.45-60 WCF / .45-60 Winchester
Warning! Notes: Velocities instrumental at 7.5 ft. Rifle: Winchester Model 1876 with 28-inch barrel. Cases: Winchester .45-70 brass trimmed to length, neck sized only. Primers: Remington 9 1/2. Over-powder Wad: 2" square of single ply toilet paper over all charges. (Handloader Issue #44)
Be Alert: Publisher cannot be responsible for errors in published load data.
Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS)
300 JHP Hornady IMR IMR-4198 28.0 1,295
Remarks: T.P. wad; energy: 1,116 fp; MAX in M-76, duplicates original; accuracy fair
300 JHP Hornady IMR IMR-4198 27.0 1,246
Remarks: T.P. wad; energy: 1,033 fp; mild
300 JHP Hornady IMR IMR-4198 25.5 1,171
Remarks: T.P. wad; energy: 912; very mild
298 No. 457191 hard .457" dia. IMR IMR-4198 26.0 1,290
Remarks: T.P. wad; factory dupl.; MAX. in M-76, Whitney, Colt's rifles
300 JHP Alliant 2400 21.0 1,300
Remarks: T.P. wad; MAX. in M-76, Whitney, Colt's rifles
300 JHP Alliant 2400 20.5 1,273
Remarks: T.P. wad; energy: 1,075 fp; good accuracy
300 JHP Alliant 2400 18.0 1,089
Remarks: T.P. wad; energy: 789 fp; very mild; good accuracy
Finally, 58 loads using a variety of powders and bullets. (no 305gr though)
.45-60 WCF / .45-60 Winchester Handloads
Warning! Notes: For use in Modern 1876 Reproductions ONLY. DO NOT USE IN ORIGINAL WINCHESTER MODEL 1876 RIFLES. A Chaparral Repeating Arms Model 1876 with a 22-inch barrel was used to fire all loads. Cases were Starline .45-70 trimmed down. Maximum case length: 1.89 inches; trim-to length: 1.88 inches. Overall cartridge length: factory loads, 2.17 inches; handloads, 2.250 inches. Bullet diameter: cast bullets sized to .458 inch. CCI BR-2 Large Rifle primers used throughout. Temperature during testing was 18 degrees Fahrenheit. Read entire article at loaddata.com under Load Development.
Be Alert: Publisher cannot be responsible for errors in published load data.
Wt. Bullet Powder Manufacturer Powder Charge Velocity (FPS)
292 cast Lyman 457191 IMR IMR-4198 23.0 1042
292 cast Lyman 457191 IMR IMR-4198 26.0 1199
292 cast Lyman 457191 IMR IMR-4198 29.0 1366
292 cast Lyman 457191 Accurate AAC-5744 21.0 1085
292 cast Lyman 457191 Accurate AAC-5744 23.0 1181
292 cast Lyman 457191 Accurate AAC-5744 25.0 1280
292 cast Lyman 457191 Accurate AAC-5744 27.0 1387
292 cast Lyman 457191 Accurate AAC-2015 32.0 875
292 cast Lyman 457191 Accurate AAC-2015 34.0 1005
292 cast Lyman 457191 Accurate AAC-2015 36.0 1151
292 cast Lyman 457191 Accurate AAC-2015 37.5 1248
292 cast Lyman 457191 Accurate AAC-2015 39.0 1359
292 cast Lyman 457191 Hodgdon Pyrodex Pistol Pellets 60.0 1553
Remarks: two Pyrodex 30-grain Pistol pellets
292 cast Lyman 457191 IMR Trail Boss 10.5 1069
292 cast Lyman 457191 IMR Trail Boss 14.8 1256
292 cast Lyman 457191 Hodgdon Varget 31.0 883
Remarks: do not reduce
292 cast Lyman 457191 Hodgdon Varget 33.0 961
292 cast Lyman 457191 Hodgdon Varget 35.0 1043
292 cast Lyman 457191 Hodgdon Varget 36.5 1089
292 cast Lyman 457191 Hodgdon Varget 38.0 1154
292 cast Lyman 457191 Hodgdon H-4895 30.0 848
Remarks: do not reduce
292 cast Lyman 457191 Hodgdon H-4895 32.0 931
292 cast Lyman 457191 Hodgdon H-4895 34.0 1044
292 cast Lyman 457191 Hodgdon H-4895 36.0 1160
292 cast Lyman 457191 Hodgdon H-4895 38.0 1272
292 cast Lyman 457191 Hodgdon Triple Seven FFg 32.0 1164
Remarks: charge by weight
330 cast HP Lyman 457122 Accurate AAC-5744 20.0 1044
330 cast HP Lyman 457122 Accurate AAC-5744 22.0 1119
330 cast HP Lyman 457122 Accurate AAC-5744 24.0 1205
330 cast HP Lyman 457122 Accurate AAC-5744 26.0 1284
330 cast HP Lyman 457122 Accurate AAC-2015 32.0 1074
330 cast HP Lyman 457122 Accurate AAC-2015 34.0 1141
330 cast HP Lyman 457122 Accurate AAC-2015 35.5 1192
330 cast HP Lyman 457122 Accurate AAC-2015 37.0 1252
330 cast HP Lyman 457122 Hodgdon Varget 28.0 819
330 cast HP Lyman 457122 Hodgdon Varget 30.0 924
330 cast HP Lyman 457122 Hodgdon Varget 32.0 1031
330 cast HP Lyman 457122 Hodgdon Varget 34.0 1144
330 cast HP Lyman 457122 Hodgdon Varget 36.0 1248
330 cast HP Lyman 457122 IMR Trail Boss 10.0 992
330 cast HP Lyman 457122 IMR Trail Boss 12.0 1065
330 cast HP Lyman 457122 IMR Trail Boss 13.0 1098
330 cast HP Lyman 457122 IMR Trail Boss 14.0 1143
330 cast HP Lyman 457122 Hodgdon H-4895 27.0 881
Remarks: do not reduce
330 cast HP Lyman 457122 Hodgdon H-4895 29.0 985
330 cast HP Lyman 457122 Hodgdon H-4895 31.0 1086
330 cast HP Lyman 457122 Hodgdon H-4895 33.0 1177
330 cast HP Lyman 457122 Hodgdon H-4895 35.0 1267
330 cast HP Lyman 457122 Hodgdon Triple Seven FFg 32.0 1167
Remarks: powder by weight
300 Sierra JHP Accurate AAC-5744 24.0 1206
300 Sierra JHP Accurate AAC-5744 25.0 1236
300 Sierra JHP Accurate AAC-5744 26.0 1278
300 Sierra JHP Accurate AAC-5744 27.0 1310
300 Sierra JHP IMR IMR-4198 25.0 1075
300 Sierra JHP IMR IMR-4198 26.0 1124
300 Sierra JHP IMR IMR-4198 27.0 1175
300 Sierra JHP IMR IMR-4198 28.0 1219
300 Sierra JHP IMR IMR-4198 29.0 1276
Hope you can use at least some of this.