Bump firing can be done with many unmodified semi-automatic firearms, though I hear special bump-stocks can increase accuracy and rate of fire. A trigger crank

Bump firing can be done with many unmodified semi-automatic firearms, though I hear special bump-stocks can increase accuracy and rate of fire. A trigger crank is pretty easy to construct. There are few moving parts, and nothing needs to withstand heat or high pressures. Other limitations such as magazine capacities and bullet buttons[1] are also easy to circumvent (the San Bernardino shooters did so[2]). Most firearm components are simple pieces of metal and plastic, so it's hard to stop people from making illegal modifications. It's also hard to discover such modifications before the lead starts flying. The police can't go into every home and inspect every firearm. For the most part, these sorts of laws serve to annoy law-abiding people while slightly inconveniencing criminals. That said, trivial inconveniences might make a difference. I doubt most criminals are willing to invest the time and effort needed to make reliable modifications to their weaponry. 1. https://en.wikipedia.org/wiki/Bullet_button https://en.wikipedia.org/wiki/Bullet_button 2. https://en.wikipedia.org/wiki/2015_San_Bernardino_attack#Investigation https://en.wikipedia.org/wiki/2015_San_Bernardino_attack#Inv...