Making high cap magazines illegal isn't going to stop someone from obtaining or even fabricating a 90rnd drum mag for their rifle. Making a 5 round limit is ridiculous, they wouldn't be able to stop hand loaders from loading. And all a limit will do is make the criminals have more bullets than you and law enforcement.
Fine take away the bullets someone will just use their powder and a jar of spare change to make an IED. Take away all that, still wont stop someone from plowing down a dozen people in their SUV, and guess what I'd bet an SUV could kill faster than most automatic weapons with high cap mags. These laws do nothing for the honest people. A crazy person will find a way to cause mayhem either way.