I’ve been looking around for some different rubber band gun options and came across this site, rbguns.com
They have detailed PDF plans for free download for making a variety of different guns. Videos showing them in operation too. I particularly like the lever action rifle, and the lever action works too!
I think these plans are best suited for someone with a laser cutter, but I thought I would share anyway. If I get enough time I want to try my hand at one of these.