I think you MAY be able to use them... assuming that with the tricky little plastic pointed tip, you can load them to a proper seating depth and yet still make them fit in your .45 Colt cylinders with enough clearance to spin freely.
You are correct...those slugs are designed for extreme pressure and velocity in the .460 S&W Mag. I think a better choice than loading them in .45 Colt, given the high price of those bullets at retail -- would be to swap them to someone who loads .454 Casull or .460 S&W Mag... or stash them in your supply until
you find yourself down the road with one of those monsters.