PELLET GUNS FOR PEST CONTROL?

i tried all of the shelf poisons and they are still here , some snap traps work but not a lot , i am trying the cage traps but since i cant release them and i livce in the city i was wondering about using a pellet gun to put the buggers out of their misery , i was wondering if the pellet handguns which have less fps than the rifles are as noisey as the rifles and if they are able to kill the buggers like what is the minimum fps needed to dispatch the buggers?