Need help Identifying some cartridges

Hey all, I recently got a load of casings from another collector and while most of them are identifiable by the caliber on the headstamp or matching with identical ones, 4 of them have stumped me. Even with searches I haven’t found an answer. Photos provided have reference cases, .223 remington to the left and .308 winchester to the right.

Cartridge 1: Headstamped FC (top) 04 (bottom)

Cartridge 2: Headstamped 06 (top) 19 (bottom)

Cartridge 3: Headstamped PS (top) 75 (bottom)

Cartridge 4: Headstamped MF (top) 7(left bottom) 55(right bottom) I’m pretty sure this one is a .303 but I’m interested if the 55 dates it to 1955

Many thanks if you guys can identify these!

Welcome to the IAA. Many of us started out as “accumulators”, and then became “collectors” when we found things we couldn’t identify and had to find out what they were. You’re in good company!
To your rounds:

  1. Appears to be a .300 Blackout or Whisper, made from a Federal 5.56 case.
  2. Chinese 7.62x39
  3. South Korean .30 M1 Carbine
  4. Australian .303 from 1955

Thank-you very much!