I have shot squirrels with both a 22 LR and a 32 and the 32 is far more devastating, but as Dan stated you need to head shoot anyway. When we use a ML we are really trying to experience what GGGgranddad did back when. Problem is we cannot. My feelings on the small bores is that they kind of fit in that category of rifle we used to call trappers rifles, like the 25-20 and 32-20. both worthless for much of anything by todays standards but fun to shoot. Today the ML 40 is not considered a deer caliber. We have been contaminated by modern experiences and modern thinking. I suspect when GGrandad went hunting before game laws and what not, he shot what opportunity presented, be it squirrel, coon, turkey or deer. The small bores gave them something that worked on about anything an Eastern hunter would encounter. I remember last year sitting at the base of an oak waiting for a grey squirrel when a little spike buck walked through feeding on acorns. Had this situation occured before game laws, I would have had a fat little spike as he came with a few feet of where I was sitting whether carrying a 32, 36 or 40. That was how the old "trapper" calibers I mentioned were used. Today we like to use "specialized" rifles and own several. Were I to own one rifle to live off the land, where game laws do not exist, the 32 would work under the conditions I have encountered, although I still would prefer the 36 or 40. Out west you would want something a little bigger. By the way I had no problems handling the small buckshot to load the 25.
DP