I would get the gun with the barrel on a sandbag and the frame shoved into it, and nothing touching the bottom of the grip frame.
This is key regarding gun setup.
Still, your 125gr groups look good. Frankly, I would say the 158gr bullets are NG. You might try another 158gr bullet, or a different diameter. Powder, as long as you are choosing basically the right one, will be a smaller issue. Also, I did not check the loads. If these are mid range, I might try working up a load. Otherwise, get new bullets. . . .
Bullets will generally be the reason why groups are completely different.
With lead, bullet size (dia) and hardness can have as much impact as who made them.