Today somewhat sums up my quest to solve a few mysteries regarding the 44-40's accuracy at and beyond 100 yards with smokeless powders. I have just about kicked this dead horse as much as I am gonna kick it.
Accuracy, at higher velocities than factory loads, can be achieved using Reloder 7 and remaining near SAAMI max pressures. It may take you some time to find that sweet load and bullet combo for your firearm but I certainly do believe you can find it.
I have been getting consistent 4" groups @ 100 yards using various bullets and loads. The latest has been with Accurate's 43-208A, Winchester's JSP and Speers 240gr DCHP.
First, Winchester's 200gr JSP's are getting scarce and hard to find without spending a fortune and my surplus is gone. My scope on the MGM 20" testing barrel platform is set for 240gr bullets. Shooting the JSP's, impact is 6 1/2" below POA. However, ten shot groups come in at 2 1/4". My pressure data shows an avg of 10,601 psi falling just below SAAMI max pressures (11,000psi). Your mileage may very. One reason these pressure are low is due to the bullets .425" diameter.
Second, Accurate's 43-208A, my hand cast loads, pleased me @ 3 1/4" groups at 100 yards replicating original black powder velocities border-lining SAAMI max pressures coming in at 11,304psi. These pressures too may be due to the bullets heeled .427" diameter with the exception of the .429" driving band flange. I feel Ed's 43-200Q would give similar results.
Third, Speer's 240gr DCHP. These pressures are a bit higher than SAAMI's max by about 4,000psi. Plenty safe for the Marlin 1894CB but I won't be using them in my weaker action firearms although I have tested 14,000psi black powder loads. Accuracy is extremely promising coming in at 2 1/8" group.
44-40 Website - https://sites.google.com/view/44winchester/chasing-the-44-40