After some of my earlier searches, I’m not surprised that Amazon Japan occasionally recommends porn novels to me. Today’s top dirty book has an interesting title, 一発やりがい.
一発 means “one shot”, either literally, like one (1) bullet, or more generally, like a knockout punch; やりがい means “(s.t.) is worth doing”. In context, the phrase would seem to map cleanly to:
“I’d hit that”