Got a Real-World Weapon, Armour or Tactics Question? Mk. XXVIII

[Pauly]

Realistically, 1950s "PMCs" would be using arms from one of two sources - the United States, or the Soviet Union. Any other supply source would be too limited at the time.
.

You are forgetting just how big the British empire was in 1950, and how much surplus equipment there was from The UK to Canada to Australia to India to South Africa.

Also for example FN in Belgium was gearing up for post-war production, starting the FN FAL. For a PMC there are plenty of options, not just the superpowers