Here's something I'm currently working on. Not full auto, I have some ideas how to do that, but looking to get this done first. Body is working out to be around 3 lbs, 1/4 inch sheet metal, two halves that I plan on bolting together at stress points, and also to get at the valve system should it ever need maintenance due to leaking or replacing the valve. The mags will be fused pvc casing, with spring loading almost double stacked, holding about 20 shells. The shells I have been making with 3/4 inch thermal paper inserts. They hold about 23-25 bbs each and have thin plastic sheet glued to the front and back, which easily break through with bbs, but hold up to handling and storage in a standard shell holder. I have a few miscellaneous gas valves and tanks, but it just seemed like the simplest method to mount a hookup for a co2 in the stock. Might even make a smaller version that will take 4-5 shells and a 12 gram pod. Working on a drum mag here and there. Let me know what you think guys. Thanks.