Changing a magazine could mean life or death for someone in those circumstances. It might mean the person is stopped by interference from authorities or civilians, it's a brief period of vulnerability. It might mean someone flees or whatever, I don't know. It's kind of ridiculous to even speculate to be honest. In general I don't see the purpose of large magazines for the civilian population anyway but I'm one of those weird Republicans who doesn't "get" the gun culture in this country anyway so *shrug*
Personally I think it's going to be a combination of factors, not any single initiative but most importantly people have to stop worshipping guns, it all starts with the underlying culture. That could take generations.