Any equivalent current powder to Sharpshooter? What kind of performance did these rounds achieve (or at least were advertised to achieve)?
Hard to say what is "equivalent" because of so many variables. However, there are powders that can be used and all are published in Lyman's 49th.
44-40 Smokeless powder transition years can be found here:
https://sites.google.com/view/44winchester/powders/smokeless-powders-transition-years?authuser=0
This is were we separate the 44-40 as a "rifle cartridge" and a "revolver cartridge". While Colt was not approving smokeless loads in their revolvers until 1909, Winchester had been manufacturing this HV load for their Model 92' since 1903.
For rifle use, to be able to replicate accurate normal loads at longer distances or to replicate HV loads, one must use mid-range rifle powders. Reloader 7, 2400 and IMR-4227 best fit the bill. For HV loads, 2400 and IMR-4227 are best. You can not get enough Reloder 7 in the case to reach HV velocities.
A published 23.5gr of Reloder 7 with a 240gr...yes, 240gr lead bullet will give you 1,250fps at less than SAAMI max pressures. This is an unpopular powder because guys don't like the left over powder, called "skeletons" that stay behind in the barrel, chamber and anywhere else. Small price to pay for the best accuracy when properly loaded with a 220gr lead bullet @ 1,350fps. The powder burns too slow for revolvers and velocity suffers.
2400 and IMR-4227 were mid-range rifle powders years before they adopted the "Magnum" name. IMR-4227 is what I use for 260 yard shots at nearly 1,700fps in my Marlin 1894CB.
Here are my test results and the loads I call me "go-to" loads because of my test results. They include the popular Lyman published max loads.
https://docs.google.com/spreadsheet...ko5yReJ9a-ER32YsENTgJGJs4/edit#gid=2085097263
It is extremely important to understand that the shooter can exceed the strength of the firearm before any of the popular "over-pressure" signs can be seen on the 44-40 cases.