In many scenes, the flat 'slab side' upper receiver of the original M16 (AR-15/SP1) rifle is seen. Some of them appear to be genuine civilian AR-15/SP1s and aren't seen fired full-auto. Instead, M16A1s seem to be used to depict full-auto fire. That is, until the Grenada sequence, when the Recon platoon's weapons are both M16A1s and M16 rifles, possibly AR-15/SP1's converted to fire full-auto, perhaps to to a lack of enough M16A1 rifles for those scenes.
What's the language limits of this site? Just to be sure.
Seen in the hands of several Recon Marines, used when a fully-automatic weapon is required early in the film, until Grenada when possibly all the weapons were converted to full-auto fire, perhaps do to a lack of M16A1s.
One of the Marines has an AR-15/SP1 (or possible M16) fitted with an underslung Colt 37mm flare launcher, made to take the place of the HE M203 40mm launcher.
Used by Recon Marine Private Johansson "The Swede", Used inside an armored vehicle by the Cubans, and seen on the helicopter that picks up the Recon men after the operation is complete.
Gunnery Sgt. Tom Highway (Clint Eastwood) uses an AKM to teach his recruits in basic training, by shooting at them so they know the distinct sound of an AK-47 being fired at them. Several Cuban soldiers use them as well, just as Highway said they would.