So in order to differentiate the SMG from all other weapons, I've was thinking of making the SMG sub-type the "gamble" gun.
It will have a huge variance in it's potential damage making it unreliable. The further the target the larger the variance in damage. This might actually in-fact promote the hit and run style its designed to do as you're fishing for the big hits, if you don't score a big hit, you run to cover.
So, yes RNG in my competitive gaming, for the sake of fun and balance.