I'll explain it best I can why the 40cal is my choice of caliber. I live in SC where we have a season that is 4 months long for muzzleloaders, so we are not under pressure to pull the trigger on a low percentage shot. Our legal muzzleloader caliber for deer is 36 cal and up, Our small game muzzle loader calibers is 40cal and smaller. Also hogs may be taken with the legal firearm during any season(All this is WMA Land Rules, Private do what ever you want).
But to get into the debate about why 40 cal. or why not. Would you shoot a deer with a 62cal? I'd presume most of all would say yes of course...At 350 yards? Most I would think say no no way. Why not? because the ability to accucuratly place that shot with terminal effect is low percentage shot. Person to person is different, by eye sight alone then throw in the accuracy of your gun and sites options, and the shooters ablity, each hunter and gun must know there limitations. Punching paper tells you how consistant you can place your shots and is where a lot of hunters start saying ok My gun has the power to shoot ???yds but me behind my gun I'm only good at ??yds. I estimate that 40cal round ball thru the lungs of a deer will kill it, would be nice if that ball would go all the way thru so to have more of a blood trail. If not just wait to hear the crash then go pick the deer up, if you don't hear the crash wait 30mins to 2hours before quietly blood trailing is all I got to say.
I'm looking into a slug for the 40 cal (for blood trails) but expect to just use the round ball, keep shots short because the eye doctor told me my eyes are normal now....Well if this is normal I feel sorry for you guys not being able to really see.