I don't play video games and I have "tons" of ammo for the most common weapons you will find, 223/5.56 , 9MM and .22LR. I don't need tons of ammo for stuff I don't have. And if you would read what I said earlier, the sole purpose of having a few rds in common calibers is to have an operating weapon to help you acquire the weapon you want. But in an end of the world situation, most likely someone would just kill the person who had what they wanted instead of trying to hijack it from them.
Your end of the world scenario is based on what?
So, how many "common calibers" do you stockpile 5-10 rds?
I guess there would be no need for 10 rd capacity limits in the apocalypse if all you have are 5-10 rds of any given caliber.
Do you think 5-10 rds is enough to get a replacement for a broken firearm, or for that matter to avoid being killed, if someone with more than 100 rds with a working firearm wants your ammo?
I still don't understand how having a small amount of AMMO for weapon you have not "come across" is beneficial. Is it your belief that weapons of "common calibers" will be abundant in the future apocalypse simply based on them being "common" now?
Large groups will hoard any weapons they "come across" for survival, either to use against threats, to take what they want, or trade for what they need.
Tell you what. Forget everything I posted above. You do that. I'm sure you'll be fine if/when your only firearm for your ammo stash breaks. I'll even loan you a gun myself. Just send word that you have lots of ammo and no firearm for it, and I'll be right over!