What type of ammunition should be used in the M4 Carbine for engaging targets at longer ranges?

The M4 Carbine is designed to use 5.56mm NATO ammunition, which is ideal for engaging targets at both short and longer ranges. The 5.56mm round is optimized for the effective engagement of personnel and light vehicles, providing a good balance of velocity, accuracy, and terminal performance at distances typically encountered on the battlefield.

While there are other calibers that may be effective for long-range engagements, such as the 7.62mm NATO or .50 BMG, these cartridges are not standard for the M4 and would not be compatible with its design. The 9mm Luger is primarily used in handguns, making it unsuitable for the range and engagement capabilities of the M4 Carbine. Therefore, the 5.56mm NATO is the appropriate choice for maximizing the effectiveness of the M4 at longer distances, ensuring that infantry squads can engage targets accurately and effectively.