the only class of mine that uses SP is my intervention sniper class, which also has FMJ (overkill and pointless i know but oh well lol)
no other class uses SP, i dont really notice much difference in how well i do not using it, does it really make any difference or is it just a placebo perk?
Go and try the ACR with and with out it then post again

It does make a difference, it's probably on like one bullet on most guns though. Do what I said with the ACR and it'll prove it.