I remember when I was a youngman going hunting with my dad. He would take 6-8 shotgun shells for his single shot 20 gauge. For years and years this did just fine for him.......... Then the day came we were hunting and had a mixed bag of squirrels, grouse and rabbits. He brought 8 shells and shot all of them long before the hunt was over. I kept on hunting until I reached the legal number of animals I could gather for the table. As that was I almost ran out of ammo myself and I carried a light load of a mere 35 rounds.
Now he carries atleast a box (25) and a 22 pistol for that rabbit that sits there thinking "he don't see me" and 50 rounds for the pistol.
I might only need 3-4 rounds, but I sure as hell aint going to carry 3-4. Minimum I carry 29. If I have the BUG (always have it) on me, I have 22 for that and if I travel long distance add a 14 round mag of ball and a box of 50 somewhere in the car. Seems like alot but it realy is not. It is 2 mags extra for the primary and two for the BUG at max. Typicaly it is one extra for the primary and two extra for the BUG