I'll add that the choice of BB weight affects things as well. My CA M24 shoots about 420fps with .2 (315fps w/ .36g) and with full hop up, I get .30g BBs out to about 150ft before the fps drops to the point that wind and hop up take over sending the BB of it's path. Shooting the same way with .36g, generally I'll get well out past 200ft before the BB drops (I HAVE hit a 12" tree trunk a few times at 230ft away using .36g BBs).
Sniping in airsoft is a hell of a lot more than just using a bolt action gun, or being able to out-range AEGs. Has a pretty widespread mental game attached to it as well. Like basic sharpshooting when attacking a defended base, scouting ahead of a team, harrassing fire from various ranges, etc. Last game day I played, I crawled into a spot about 20mins ahead of my team, a small ridge maybe 150ft away from the nearest wall of a large base we were attacking. Wind was pretty bad from the south, I was west of the base, and couldn't hit crap all due to it, even with .36g BBs. So, all I did was lob shots at all four walls, keep guys guessing where I was and to keep their heads down while my boys attacked. Even from 300ft away, teammates could hear the loud SMACK of my .36s hitting walls. When the game was over, one guy asked if I was located south of the base (I wasn't) as he could hear the rounds hitting over there. Basically I just harrassed the heck outta them. Nothing really sniper that game, just I crawled into a good spot, and used my range and heavy BBs to do my thing. No one took a shot my direction (once I was the last guy alive, they hunted me down and swarmed me), even after one of the tower guys spotted me. I just moved 30ft along the ridge to a more secure spot.
Some genius (either not understnading the 3D aspect of sniping as a whole, or only having a full 100% knowledge that airsoft is a "Ballistic experts WORSE nightmare!) claimed that "There are no snipers in airsoft, only lucky shots!" Well, there is some truth in there, but a lot of other things add together to make an airsoft sniper an airsoft sniper. Not just about the gun you use, or the range you can shoot it from. A lot has to do with field craft, etc. same as has been mentioned above.
And, notice early on I said what my bolt action shoots at, and the range I can get heavy BBs out to. Relies a lot on the amount of hop up used, as well as the 6.03mm barrel I have. Not really fps dependant in some cases. Am sure that if you took an upgraded 450fps AEG, put enough hop up on to send a .36g BB flying a long way, that you'd get virtually the same effect. Can't claim that for sure though, since I have yet to personally come across that hot of an AEG, but am sure it helps with your question.