The A-10 Thunderbolt is known for its massive gun - the GAU-8/A Avenger cannon. A 30mm cannon that, with ammunition and feed system, weighs over 2 tons. Each 30mm round is close to 1 foot long and weights 1.5 pounds, and the 1,150 rounds are fired at a rate of 3,900 per minute.
As you might imagine, loading over 1,000 heavy rounds involves some heavy equipment and teamwork, and this video gives you an idea of what goes into rearming this massive weapon system.
Like the video said, the A-10 Thunderbolt was essentially designed around the GAU-8/A. Looking at the aircraft from head-on, you can see that the firing barrel is inline with the aircraft's center line, and the nose wheel has been moved off to the side to accommodate the large cannon and its ammunition drum.
This is not only to improve accuracy, but if the firing barrel were off to one side, the massive recoil (about 10,000 pounds worth) could cause a significant yaw effect, pushing the aircraft off target and causing stress on the airframe!