Well, originally, Vietnam had almost a million of them. They sold or gave much of them away as military aid to their fellow Marxists, especially to Latin America. For example, did you know that Vietnamese ‘16s were used by the El Salvadorian FMLN, the Guatemalan URNG, the Colombian and Honduran anti-government forces, the FPMR of Chile and the Nicaraguan Sandinista govenment?
I remember seeing a semi load of M-16s that had been captured from Salvadoran guerillas. Many of them had the mag housing corroded badly. There were a series of photos of a Vietnamese “arms dump” on some site a couple of years ago that would make a collector cry. Huge heaps of rotting, rusting guns of every type just piled up in an open field. Most of the wood stocks were rotted clean away.