Sniping in airsoft is not limited to bolt action guns (but it's more realistic). I normally used my AK47 on single shot and it had plenty of good range. If folks ignored the hit (it happened), I'd simply flip the switch to full auto. Trust me, they never ignored that.
Unfortunately some of the worst offenders happened to be among the most 'experienced'.
Sniping is a technique. What you use only needs to have some decent range and accuracy. I strongly suggest you listen to Stalker's advice, he knows his stuff.