I've got about 500 55gr Hornady SP's (Garage sale bagain)
I'd like to give them a little more explosive power. So I'm going to make a Jig to drill a hollowpoint(I'm a Toolmaker), Question is how deep do I go? or how about taking the soft lead point off to make a mini WC?

Knocking off the lead tip will not pose any sort of a problem at all, other than potentially increasing weight variation among the bullets.

As for hollow pointing, I suspect you can go as deep as you wish, all the way to the cup if you desire. Personally, I would stop about .080"-.100" deep.