In normal flight, the gun is hidden behind a retractable panel, so it doesn't take away from the plane's stealthy profile. F-35 makers at Lockheed Martin say the gun "will provide pilots with the ability to engage air-to-ground and air-to-air targets." Since pilots have it, that's invariably how they will use it, but it's likely to be a worse tool for attack than the guns on the planes the F-35 is replacing. The 20mm gun carried by the F-16 fighter-bombers deploys a smaller round each burst, but it also carries over 500 rounds of ammunition to battle. The F-35 is also replacing the A-10 ground attack plane, whose powerful 30mm cannon was fed by a magazine holding 1,350 rounds of ammunition. As it replaces both of these planes, F-35 pilots will have the gun as an option in battle, but to win a fight, they may need to rely on other weapons first.