The Commando perk offers significant bonuses with automatic weapons. Depending on the rank, you may inflict more damage, gain improved hip fire accuracy, or stagger an enemy.”— Fallout 4 loading screen hints
The first rank of this perk increases the damage of automatic weapons by 20%. The second rank increases this bonus damage to 40% and improves hip-fire accuracy with automatic weapons. The third rank increases the bonus damage to 60% and improves hip-fire accuracy even more. The fourth rank increases the bonus damage to 80% and gives automatic weapons a chance to stagger enemies. The fifth and final rank raises the bonus damage to 100% and increases the chance to stagger enemies.