Billy,
Boyes is 55 cal not 50, unless you have a necked down version and recoil is not off the scale from where I am sitting -it weighs close to 35lbs. I know teenagers who fire them.
Of the firearms you mentioned I would say the 600 on the heym would load up to the nastiest recoil by far.

You are joking about 50 BMG's making inroads to African game hunting aren't you?

Karl.