Nobody believed Ripley. Burked only took a shot in the dark just to see if she was legit or not.
They still went in with Smart guns and nukes though...
Smart guns would just be the future equivalent of the automatic rifleman. In the Army only two people per squad used to carry automatic rifles, and that would've been your saw gunner, as the M4s used to be only semi auto.
Presently most frontline units have m4a1, so technically everybody has full auto capability, but the SAW and the Smartgun would have higher rates of fires, and with the bipod/tripod the m249 uses and the chest harness the smartgun uses, they would be able to control those higher rates of fires better than the standard rifleman would with the m4a1............and the m41a.
Nukes all seemed to be under lock and key aboard the Sulaco.