Other mistake: Near the start, instead of showing bullet casings drop they show full bullets drop from the gun on the ground. (00:12:44)
Suggested correction: The shell casings appear to be unfired, but this is only because of the lighting and angle. Upon closer examination they are empty 5.56mm brass as they should be.
Other mistake: All their wounds heal immediately and preventing wounds from closing is painful, but Andy has earrings the entire time and Nial has earrings in the final scene.