I was going to ask this question as I was looking at pack weight for an upcoming goat hunt. Glad I did a search.
I have been carrying 10, this goes back to a gun that held five in the mag plus a reload. New rifle and I only carry four in the gun now, but 10 still feels right.
For my revolvers I carry 12, six in the gun and six for reload. I figure if I'm charged by a bear and happen to be left breathing, odds are good I will have emptied what was loaded in the gun, so a full reload is in order. I rarely carry both a rifle and a revolver though.