>>713922598
That's an M16A1 carbine.
Essentially Vietnam era gat. No more out of place than an AK or G3 wannabes.

Fallout 1 already had a fucking DESERT EAGLE and FN P90; a 1980s and 1990s firearms.

>>713922894
1950s - 1960s retro future, you dork.
"Atom Age" for a reason.