Primary crux solves the reload problem in hip fire so long as you get 1 headshot every 10 seconds ish.
Edit: clarification, this is for the ax 52 as the 60% ammo efficiency stacks with the 40 for hip fire so you don't spend any ammo at all so long as you headshot
I go acuity and primary crux for pure hipfire, if you want to optimize for ads, multishot and deadhead might the the better option, with scope giving you even more crit chance