Checking Lyman 50 for 45 Colt (Rifle Data)
16" 94 Win. and 20" Universal receiver for Vels
For 185 JHP (Sierra) they show
W231 (HP38 is the same powder) Start 7.6 1021fps MAX 8.5 1111fps
N320 Start 8.3 1102fps MAX 9.3 1289fps
For a lead 255gr they show
W231 Start 6.5 930fps MAX 7.2 996 fps
N320 Start 5.8 790fps MAX 6.7 941fps
(only real diff between rifle and pistol data is vel due to longer rifle barrel)
Scratching my head a bit about why the MAX with N320 is higher with the 185 as N320 is faster burning than W231 but thats what it shows.
Hodgdon shows with a lead 250
Winchester 231 .452" 1.600" 5.8 785 9,100 CUP 7.1 916 13,900 CUP
(Pistol data 7.25" barrel)
Slowest powders Hodgdon shows are Autocomp/CFE-Pistol, Lyman shows HS6
N350, 3N37 are a little slower that Autocomp, N340 a little faster (from the burn rate chart I am looking charts vary and of course are "closed bomb" tests)
For VV powders N330 is close to Unique on the burn chart, N105 probably closer to 2400 than N110
VVs burn rate chart
Forget when I got the VV .pdf but it is a couple years old.
On a target that size with a good load it should be doable, if the shooter does his part.
With a shorter zero and irons hold over will be fun