I got addicted to firing heavy cubes at (and through) sheetmetal. A few close calls convinced me to take a break, but I miss the destruction terribly My thoughts go like this (only more right-side-up like) : Based on the M10 hexnut gun, the magazine and barrel are opened up for the .750 inch ammo. The center layer will be made of .750 plywood except under the barrel (in yellow). The cubes will ride on a strip of UHMW plastic that is impregnated with Teflon. Think cuttingboardspeedzilla. I learned about this material at work and want to test its durability. Its as slick as deer guts on a glass doorknob, but the test will be if it holds up well enough. Also in the picture is a test replacement for paracord made from very thin wall stainless steel tubing. The OD is about .188inch and is pretty light. Its bent in a loop and fixed with electrical shrink-insulation . I plan on beefing up the slide to .750 thick, plus adding a chest plate and handles for both hands. I want this gun to fire through several layers of thin steel with a decent fire rate. I would love any input from you guys as this will be only my second launcher after building the M10 hexnut gun.