Do amatures count? That's my 25mm French Puteaux AT gun in my avatar photo. Regularly shoot it at events around the country. Mine's only about 100,000 ft/lbs of muzzle energy. Still wouldn't want to get in the way of the recoiling breech.
I'm the small kid on the block. Here's a video of some of my friends & fellow shooters and their toys. Cannons, machine guns, flamethrows, oh my!
Sometimes it's amazing what is in private hands.
Extreme Shooting with Damage.llc Video