I never really thought about the twist needed to stabilize the 450 gr Lyman. Intersetin g it comes out at 36".
The Sharps made 50s (and Shilohs to at least #10000) had a twist of 1:36. The 50-2 1/2" shot a 473 gr bullet but it was usually PP and these stabilze a little easier. However, none of the 50s were noted for very good accuracy. Due I am sure to the marginal twist. I believe Sharps stated in print that the 44-2 5/8" shot better at 1000 than the 50 2 1/2" did at 600. I beleive Wincheser used a 60 inch twist for the 50-95 Express and something similar for the 50-110 version.
I always considered the 50s to be hunting rounds with accuracy being good enough for that purpose. This is based on my experience with Shiloh's.

Modern reproduction SS with faster twists, 1:22 or maybe 1:24 seem to shoot very well, as they should. I have often wondered at the gov'ts slow twist and why Sharps did not increase the twist somewhat to maybe 25 or even 30.
It just occured to me that perhaps the rifling machines used by the gov't for the job, certainly the same ones used to do the Minie ball muskets, may have needed a major rework to get faster than 42"??? Seems silly in this day and age but it could have been as simple as that. Or somebody goofed when doing the twist calculations.

Dan