I've fired 45 and 50 cal pistols, they have quite a kick. It's pretty interesting to go to a range and start with a 32, then 38, 9mm, 40, 45, and then 50.

40 isn't much more kick than 9mm (for one round - shoot a few and you notice the difference), but 45 is noticeably more, and 50 is, as they say, "a freakin' hand cannon", in a much heavier/longer gun to boot.

So a double 45 would probably be more kick than a 50, though I'd have to look up some numbers and do a little math, keeping in mind a small increase in kinetic energy translates into noticeably more kick as your hand/arm have to control peak acceleration/momentum.

So it would be every bit double the energy of a 45, in the same grip, so would likely feel a lot worse.