During most of the show, soldiers and police use M16A1 rifles, but there are events in which the M4A1 Carbine is being used by multiple characters. The show is set in the early 80's, the M4 first went into service in 1994.
In one scene there is a 5th Generation Toyota Hiace Commuter in the background that came out in 2004 & in another scene they boarded a KingAir which had winglets, Beechcraft did not add them until 2011.