I like CCI's segmented HPs, copper-washed. I used some Remington stuff yesterday, though, that worked OK, Had a few FTFeeds, though. Not had that with the CCI stuff, I just can't find the CCI anywhere.
I'd be careful, I was once informed that owning subsonic rounds "isn't normal" and they are "only used to kill people" WHO ARE YOU TRYING TO KILL!?!?!?
Aguila does advice against using their "Colibri" stuff in longarms, so I don't buy them.
My favorite "full-power" subsonic RF round so far are the PMC "Moderators" (38 gr. HP).