I looked up Vit data and it does not list a 44 rifle loading on pistol loads with N110 powder.

Their starting load with a 7" barrel with a OAL of 1.602" with a 240 gr bullet was; (2nd hand data )

Starting load: 20.4 grs at 1427 fps.
Full load: 22.1 grs at 1541 fps........ with N110 powder 44 Magnum load.

A 20" barrel should get 1,750 fps with no problems, with this slow powder.

Good luck with your test and loads.