I don't own a M52 (although it is highest on my list of "grail" guns), but I have known several people that used them regularly in bullseye/NRA pistol competition.
Almost to a man they all used Bullseye powder with a 148gr wadcutter and used slightly above starting loads as listed in various reloading manuals.
Basically, they begin with the starting load listed (depends on manual of course) and work up in 0.1-0.2 grain increments until they get 100% function of the gun. Once proper function is assured, many of them will experiment with heavier loads (while staying within book recommendations) looking for an accuracy "sweet spot" that still functions the gun without battering it.
This is the same method I use to develop target loads for my "non-52" pistols and it has served me well for a long time.
I guess my bottom line point is that all pistols (and in particular Model 52s) are a law unto themselves when it comes to function and accuracy, and it may take a bit of experimentation to find what's best for you in YOUR gun. If I HAD to make a hard recommendation on a powder though, I would strongly steer you towards Bullseye. Other, newer powders may (and probably will) perform as good as BE, but I have used it for so long that I am comfortable with it.
TRE