Is that a......Tire?
I'm an old Cannon Cocker. I've worked with and around everything from SP to Towed to Mortars. 4.2 inch, 105mm, 155mm even the old 8 Inch guns (which were beasts in every sense of the word). I've never seen an artillery piece quite like this one but anything that shoots a tire with a resounding boom and a cloud of smoke is flat out awesome.
I think I need it. I at least have to shoot one though perhaps with a slightly longer fuse. I gotta drop an e-mail to The Redneck Engineer and put a bug in his ear.