No need for reduced loads, unless you are worried about noise. Just load some FMJ's to standard velocity. I have loaded hornady's 55 gr. FMJ for my encore pistol, and while they win no records for speed, they do shoot right through anything, including squirrels, without making a mess. Just whatch what is behind your target, as they tend to ricochet very easily if they hit a hard surface at any angle.
As for the "other" squirrels, like the P.O.S red squirrels and woodchucks that keep digging holes in my barns, I bust out the 257 weatherby using the 75gr vmax's loaded to around 3800 fps. What is left of them after these is not for the faint of heart.
-vanbuzen9