Look at the of how different actions work?
Transitioning from "iron sights" to LPVOs (Low Power Variable Optics).
Common standards include 5.56×45mm (NATO) and 7.62×39mm (Soviet).
Versatile systems used on bipods or vehicle mounts (e.g., M240B, PKM).
Select-fire weapons using intermediate cartridges (e.g., M4 Carbine, AK-74).
Heavier rifles firing full-power rounds for longer range (e.g., SCAR-H). 3. Machine Guns
Compact weapons firing rifle-style cartridges for non-combat personnel (e.g., FN P90). 2. Rifles & Carbines