I have a few pounds of SR-4759 powder inwhich I use quite a bit in several other cartridges. I was wondering if it would be possible to use this powder for reloading 200 grain JSP bullets in my .44-40 reloading? I am using the loads in my Rossi Puma "92 Lever Action rifle. If possible how much powder (SR-4759) should I use?? Thus far I've been unable to find reloading data using SR-4759 in the .44-40. <Thanks!>

Look at the comparable power data in comparable cartridges.

You also need to assess how strong the Puma is.

Similar burning rate extruded powders are

H4227
IMR 4227
Accurate Arms 5744

Alliant 2400 is a little faster.

Looking at the pressures of the 44 Magnum you need to stay well under the start loads for that cartridge which means your starting loads need to be maybe about 30 percent lower than starting loads for the 44 Mag. Your max loads probably need to be 10 to 15% under start loads for the 44 Mag.
Taking loading advice like this is risky business. You need to find some data for similar powders and work from there.
An old Lyman manual may be a good place to start.

If you proceed with this loading adventure don't fire the loads in a handgun or a weak rifle such as a 73 Winchester.

Thanks, ireload2