thing is theres to many variables to account for. each situation is different.
for example if you keep your reloads in a pouch held shut by a snap, you need more time. those snaps SUCK when your in a hurry. and if you make sure they dont freeze by keeping them under your coat you waste more time because you have to dig under your coat and so on.
if you want to see what a realistic estimate of the time required would be, have your buddy start blasting his boom box with metalica at full blast at 2 am when youve been asleep for 3 hours. with no lights in the room. see how well you do.