The particular pistol i'm playing with at the moment is a Reichsrevolver in 44 special, the load is 6gr of sr-7625 behind a 240gr SWC for about 800fps, that speed is based of loading manuals.
The theory behind the different loads hitting at different POI is that the heavier/slower loads will remain in the barrel longer giving the recoil time to act on the pistol slightly before the bullet exits the muzzle, a faster/lighter bullet exits before the muzzle has lifted very much from recoil.
On another forum I came across a thread where the OP complains about a revolver in 44 mag shooting very high, he considers modifying the sights or sending it back for warranty, upon calling the manufacturer the said the sights were regulated for full house 44 mag loads, after switching to mag loads from the light 44 special loads he was using to sight in it was shooting nice groups at POA.