You can get semi auto hunting rifles with a capacity of 6-10 rounds. I’m as anti gun-violence as anyone, and generally agree that more gun control is not a bad idea, but outright banning AR-15s is not the answer.
There are too many already out there to make a dent, and anyone can 3D print a lower receiver that will will hold up for at least 20 rounds.
80% lowers are a thing and you can “finish” them with basic hand tools and a drill, then you have an unregistered firearm.
There are many other ways to acquire one illegally or semi-legally, but they are currently pretty “obscure” since it’s so easy and cheap to buy a lower and assemble your own. Banning legal sales will only bolster the alternative methods.
So you’d normally say “that’s too much!” in which case the subject “that” is plural and countable so therefore “much” would be correct.
Otherwise you should say “you have given me too many refried beans!” since the beans are volumetric and not countable entities.