Originally Posted by TokyoSeven
Pain is experienced differently by everyone.
Man.... that totally could have turned into something sexual. I expected better from you T7......
OP: It's like the difference between getting hit with a hand at 100 FPS and a whip at 100 FPS. The energy carried by each implement is different.
Just for illustrative purposes lets use f=m*a (and assume equal area hit by each implement), sure the hand and whip move at the same speed but their masses are different. This is the difference between the two. Although pain perception is different there is more energy in the whip and all that energy must go somewhere. Some may be lost to sound and other inefficiencies but assuming equal energy losses the whip still has a greater amount of energy to transfer and where does it transfer to? The victim of course (which should teach them to not be naughty.....).
Anyways. Shooting at the same energy at the muzzle, a heavier BB will hurt more due to newtons first law (object in motion tends to stay in motion), this is because there is less energy loss over time/distance and therefore more energy to transfer to the target/victim after getting hit.
As for guns..... CT and Walmart are probably going to be your best bets. In Japan they have a 1J law so you'll be shooting at ~328 on .20's.... otherwise the dollar store or CT/Walmary will likely have what you're looking for. Sorry but my knowledge extends to only that extent. Not trying to be rude/elitist or anything but I really only have knowledge about "real airsoft" and not "crapsoft/softair".
What are you looking to do? If you want to plink pop cans or beer cans a pellet gun (.177 cal/4.5mm) will do the trick but if you're looking for something to shoot at each other with (with proper eyepro of course) pretty much anything from CT will do..... I guess those cheapo spring pistols from CT will do the trick and should shoot within your wanted FPS range (assuming you're looking for those velocities using .20's), if not then dollar stores sometimes have those "BB gun" things that are like $3-4 and shoot 6mm BB's at like 100 FPS (if that), hell some people can throw a pen through a chrono faster than that......