Power pistol is the canister grade version of the powder developed for the US military 9mm and as such works great in the high pressure small case capacity of the 9 producing excellent velocities and accuracy. It is a rather flashy powder in the 9mm and if you check Alliant data you will see data is conspicuously absent for lead bullets, my guess is it burns a bit hot for bare base lead.
I have tried it in the .45 acp and the .38 spl with jacketed bullets and abandoned its use for these cartridges. With even fairly stout loads in these rather low pressure cartridges it leaves carbon burning on the outside of the case. Velocity is good but the burning indicates incomplete sealing of the case to the chamber. Standard deviations was in the 18 to 30 fps range vrs 13 to 14 in the 9mm.
IMO Power Pistol is just not a good application for what you are loading. I'd suggest switching to Unique if you're looking for a velocity power factor with those MBC bullets or a faster powder like Bullseye, Red Dot, Green Dot, W231, AA#2, etc for target level loads.