When confronting the black market gun dealer about his rifle jamming, the dealer offers the shooter a "bump stock". He installs the stock in that moment, with no tools and in almost no time. In reality, the installation of such a stock would require removing the grip from the rifle (requiring tools and time) and requires specific knowledge of the construction of such a rifle.
After receiving his repaired rifle, now equipped with a bump stock, the shooter turns to the paper target and immediately lets loose a burst of fire. In reality, successfully operating a bump stock requires considerable practice and maintaining accuracy at that rate of fire needs quite a bit of training.
Upon discovering the bootleg gun shop (and empty bump stock box), Chris remarks that the shooter is out there "with a machine gun". Installation of a bump stock does not convert any rifle into a machine gun. Building a machine gun requires specialized parts (which are subject to tight regulation) and skills.
When entering the office, the shooter fires a burst into the air, gripping his rifle with only one hand. That would be possible with a true machine gun, but his rifle is not a machine gun. Rapid fire using a bump stock requires, in addition to a large amount of practice, gripping the rifle with both hands and pressing the stock against the shoulder.
In the restaurant scene, the camera focuses on a black man eating from a spoon. The second time it is focused on him, he appears to put the spoon near is mouth but doesn't actually have it close enough to pretend he is really eating. Totally blooper.