My son built a spud-gun several years ago. He and his buddy had great fun with it - launching potatoes down at the local ballfield.
What a great mother you are....all moms and dads should encourage similar activities with their sons (and daughters too if they are so inclined). America would be a far better place, populated by people who grew up learning ballistics firsthand rather than learning Marxism in the Government schools. Full Steam Ahead and Cheers to you!