For a week big game hunt with the prospects of harvesting two caribou, how many bullets would you bring?

I was thinking a box of 20 would be MORE than enough, but a friend of mine said I should bring 40. Do you see any reason to bring this many? I'm thinking 2-4 to confirm sighting + 2-4 for harvesting two caribou... that makes max 8 bullets... 20 is 2.5 times that. I'm even thinking of shaving off from that.

The reason I'm asking is I have a weight limit of 65 lbs for everything going in, so every pound counts.

Thanks