What is the overall length of the M16A3 service rifle with a suppressor?

The overall length of the M16A3 service rifle with a suppressor is indeed 40 inches (1,016 mm). This length accounts for the rifle's standard configurations and the additional length that a suppressor adds to the barrel. The suppressor typically increases the overall length by several inches but does not double it or add excessive length that could lead to the larger options listed.

When the M16A3 is configured with a suppressor, it remains manageable for tactical applications while still providing a more discreet firing capability. This design consideration makes the 40 inches the most practical measurement in terms of balance and maneuverability as compared to other lengths that would be unwieldy or impractical for operational use.