There are few sounds more welcome to U.S. military personnel than the sound of an A-10 Thunderbolt II's GAU-8/A Avenger 30mm autocannon raining down a hail of lead on an unsuspecting enemy force.

The sound is muffled with all the gear we wear ... or about the time you release the trigger,” Marks recalled. The GAU-8 is mounted laterally off-center because the recoil could move it off ...