Paintball guns can shoot faster than 300fps but you are not allowed to play over that fps, else they crack masks and could cause serious damage.
I am pretty sure the gun I have can go up to around 400fps, and when i did target practice with it I was shooting at a plastic container(rather thick) and it shot holes through the plastic.
Getting shot with a 300fps paintball still hurts, and you do bleed quite often when playing. Plus the thing is if you have a fast trigger finger you can unload 15 balls in a matter of like 3 secs or less, and if you focus on one area he wont be standing there for long.
Worst places to get shot with a paintball are the follwoing:
Naked calves (on the back of your knee or just below the fold in the leg)
Lower back
Neck
and pretty obviously the crown jewels.
5 fast shots in those areas and he will drop or run away. If you are a bad shot or it is night and you cant really aim, you do get lazer attachments for these guns, the green ones are the best as you can see them in the day as well. Plus the upside is the paintball gun can feed your boilies as well (well only if you have 16mm)