Heartbreak Ridge

The guns seen in this movie are:

M16 (AR-15/SP1)

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.

M16 (AR-15/SP1) 5.56x45mm

Recon Marines in training fire their M16s down range, although they are likely AR-15/SP1s, as they aren't seen firing full-auto until in Grenada, when more full-auto guns were required. One marine fires his weapon full-auto during the rifle training, but it is clearly an M16A1.

Gunnery Sgt. Highway (Clint Eastwood) shows his recruit his AR-15/SP1 is not "Fuckin' fucked up."

What's the language limits of this site? Just to be sure.

Pvt. "Stitch" Jones (Mario Van Peebles) with his AR-15/SP1 while Highway hassles him over pawning his kevlar helmet.

Highway with his AR-15/SP1 in Grenada. This one appears to be converted to full-auto or it could be an actual M16 fitted with an A1 birdcage muzzle break, but it's a bit less likely.