What powders do you have on hand ... Or
What powders can you beg , borrow or steal ... Or
What powders can you buy ...
It's not what is the "Best" powder ...the question is what can you get.
Lots of powders will work ... my short list :
Viht N-340
Auto Comp
Power Pistol
Silhouette
IMR 800X
Longshot
SR 4756
HS-6
AA No. 5
Blue Dot
AA No. 7
There are others but these are top w/ 155 gr. JHP
Cast lead / coated and plated bullets offer the use of several more faster powders like 700X , Bullseye , Red Dot , Zip , AA No.2 , HP-38 , Unique , Universal ... You said HP so I am assuming Jacketed HP ..
Those Pesky Details matter in handloading ... Load Safe
Good Luck
Gary