I don't think I have guns that came specifically from Vietnam but I do have guns that were in use when the Japanese/French/Americans were there.
I have a MAS 36 in the mummy wrap,a Japanese 7.7(but I think those were not used so much if at all by the Japanese in the Vietnam area)a Chinese type 53 Mosin Nagant,Russian SKS(were any sullied as aid or only Chinese and North Kirean and maybe East German?), I once read an account of a Finnish M39 being captured in Vietnam!
Must have been supplied as aid by Soviets after it was recaptured by them from the Finns.
The French left a lot of stuff over there including a lot of Nazi type stuff like P38's and 98K Mausers.
M1carbines were common. I have a commercial clone.
I'd love a MAC 50 and maybe an older model in 7.35 French long but those are hard to feed. Thenold Frech Ordnance revolvers are neat too. I want a Lebel rifle as well.