Why the hell would we limit ourselves to exactly as many as we think we might need? Unless we are on a budget, why should we let the government tell us how many of a legal thing we should be able to have? How many eggs do you eat per day? How many of those do you need? Maybe the government should limit how many of those you can have in your fridge.
I don't really care how many rounds you have in your house, or fridge, or wherever else you may keep your ammo.
I care about how many rounds you can squeeze off before having to reload. I personally don't think you need more than 10, because you can reload a 9mm in less than 2 seconds if you're practiced (and I was when I was in the Security Force at Newport RI).
I mean..............do you REALLY need the capacity to squeeze off 100 rounds with a semi automatic weapon? If so, you're stupid, because the gun will jam from the heat created at around 60 to 75 rounds.