Mattox speaks of how Murphy's armor will be able to withstand anything up to .50 caliber ammunition. This is a gross simplification since impact velocity, mass, jacketing and other factors apart from caliber will also greatly affect the effectiveness of a bullet.
In the scene where Murphy and Lewis attempt to trick Antoine Vallon into believing that they are buying weapons, he gets a phone call from the two corrupt cops to inform him of their true identity, he then orders his men to kill them both without any moral issues and the gunfight ensues. Yet in a scene a few minutes later, where the two corrupt cops meet with Vallon to discuss killing the two of them at the hospital, he is suddenly fearful of killing police officers, "Kill a cop, look over my shoulder the rest of my life."
Rick describes the M2 Battle Rifle as having a "30-round clip" when it is magazine fed. A "clip" is a device meant to hold loose rounds of ammunition together for insertion into a weapon or magazine. A "magazine" is a device meant for holding and feeding ammunition into a weapon.
During his training, Mattox tells Murphy if he senses he needs a weapon or is threatened, the visor goes down and the system makes the weapons available, yet when faced with guns in the lab, you can still see his face throughout.
When RoboCop enters the lair of Antoine Vallon, his left hand weapon is the "modified Mk.II Battlerifle". A little later on, it's an H&K MP7. When he shoots Antoine Vallon, the Mk.II pops up again only to disappear in the next sequence.
Doctor Norton says that Murphy suffers "4th degree burns on 80% of his body". The bombing scene - and the images shown of Murphy afterwards - does not convey anywhere near that kind of damage. The imagery has likely been toned down for the PG-13 rating.