If you wanted to for drop in type dayskirmishes you could theoretically have a primary (say a VSR) and carry a M16 as a secondary but you'd probably be laughed off the field, it would be bulky as hell and increase your profile when you're trying to sneak around as a scout (I'm not calling it a "sniper role" because it's moreso moving around fast and scouting for enemies and reporting back to your main group so they can engage).
For milsims machine pistols and SMG's might work but you'd have to clarify with the person running the game (whether they need your secondary to be sub 330 FPS regardless of what it is or if it's pistols only or whatever). But really a good reliable pistol that will fire every time you pull the trigger is IMO where it's at for having a secondary that you can use in CQB or if you're below the MED of your primary or whatever.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE