what is the ideal caliber of muzzleloader for deer hunting

Obviously any of the four will kill a deer. You may get a better bullet selection from the .50. The .52, .54, and .58 cal are companies offering a new product to induce sales.

Any of those will do, but the heavier the bullet, the more recoil and the faster the bullet will drop at a distance. 50 cal. is probably the most versatile.

50 cal for me...

A .45 is good but .50 is probably the best imo because of the better bullet selection.

.50cal for me!

.50 of course

i would suggest staying with a 50 cal. The reason is thats how the world is set up. You are out some where on a hunt and god forbid you loose your bullets and have to go to Luks hardwear store the chances are he will have 50 Cal not necessarly any others. 50 as seen by the pole is the most populat cal. and you can easly get anything you need in that cal a lot of the other cals you may have to order which takes time. my 2 cents

Are you asking about an inline??? Or a sidelock???
What projectile are you going to shoot??? Patched round balls?? Sabots and pistol bullets??? Or full bore maxi-balls, powerbelts etc????