Awesome catches, man!..even an MGC M16 with the correct Vietnam parallel forward assist and correct 3-prong muzzle..
Most movies get the muzzle wrong, Forrest Gump etc..Full Metal Jacket got it right though, but that was probably mostly due to Stanley Kubrick's meticulous nature..and Bapty's wondrous supply of course.
..it only took me 30 some years to get my hands on a real AR/civilian version of the correct era myself (though without any forward assist).
-Carson
The „forward assist“ on the MGC is actually just a feature to connect the lower to the upper receiver