.177 vs .22 and FPE vs FPS

[rslpellet]

Not entirely sure if this is where the question should be asked, but seems to be the more appropriate area. Me and my friend are arguing over whether fps determines a rifles kill-ability which is what my friend thinks, but I say that FPE is what it determines, so we really need a clarification. I said that an .22 pellet gun would be more likely to kill small game at 750fps compared to an .177 pellet gun at 1000fps, he thinks the .177 would win and I think the .22 would win.

So Basically which would be more likely to kill a rabbit under 40 yards, a .22 pellet gun or a .177 and should you go by fps or fpe to determine how powerful a gun is? Only 16 so everything helps

Thanks,
Rick

Oh and a reply from 11PM-7AM CST would be awesome if possible, would love to prove him wrong tomorrow before school(if i am right)

[Switchback_XT]

Ahhh so your 16 years old ehh?
Well what you need to look up is Kinetic Energy first off. Basically Energy=Mass x Excelleration squared.
So to double your Energy you could double the speed or double the mass as I understand it.
A .177 cal pellet could have plenty of "killability" at 1k FPS, if its heavy enough. Most .22 cal pellet's kill squirrels in the 700-800 fps range. I use one to protect the bird feeder and around the yard.