duly noted. I don't have a star gun exactly,more like a star mine. I can fit a handful of 5/8" stars down the barrel,lol I test out over a river and i had stars slapping off the water everywhere the last 2 mortars i launched,it was ridiculous. I'm used to rockets traveling much higher. You mentioned rubber stickies,i had that shit all over my hands and knife. Stuck to the rolling pin,and the giant clear polyethylene mats i use to work on everything. I see now how important the wax paper is now.
You can make a simple 1" x 6" stargun from a cardboard tube, hand rolled if desired. CannonFuse sells them for like a buck or two, but that's overpriced for what you get (especially with shipping). Or a piece of pipe. Simples. You just need a plugged tube that'll tolerate a few grams of BP going off in it. The usual ratio is 1:6 inner diameter/length, but that' pretty flexible. Shorter for a mine, taller for a high shot. A lot of folks use smaller even. I have 4 iron pipes welded to a flat iron base that go from perhaps 3/8" for single stars (rarely used) to 1.25" for maybe 10-15g of stars (gets the most use). Fuse holes in the bottom. A cut down 1# or 3# rocket tube epoxied to a chunk of 2x4 works fine for quite awhile. Best to drill a short hole and glue in a wood plug for the tube to rest over before gluing the tube down, for a little better durability. Super useful and you don't need to use handfuls of stars in a large mine just to test out the burn characteristics--you can do that right after! Guessing you're using a cut down 2 or 2.5" mortar, which would use up a lot of comp and be more of a show than a test platform. Smaller is better when you don't want to nick the neighbors and don't feel like slogging on down to the riverside just to test some stars. Even a 1-1.25" stargun/mortar will be reasonably eventful and not so dangerous. My 1.25'er launches 5/16 primed stars up to 50 feet with ease.
The stickies suck but are avoidable. Gloves help. Also not working/cutting it until it's "just right" is a matter of patience. Unlike DEs that turn to rock quickly after rolling out, rubber stars are more forgiving. And rolling out on a nice pile of hot prime, and dusting, hell smothering, in a little prime before rolling and then a lot of prime after rolling keeps the surfaces from being sticky. And you're going to want that prime on the sides of your stars, too, so if you have a bunch on top of your patty, it'll fall down the cut lines and help keep your knife from sticking. Prime is your friend. When you're ready to cut, maybe stop and wait a few more minutes. During that time, dump a reasonable shitload of hot prime on top, maybe lift the patty edge and toss some more underneath, and then start cutting. I've heard of folks pre-coating their blade with a thin layer of silicone oil or cooking spray to prevent sticking (and I considered it after the first few times I cut super-sticky DEs, ffs), I've never found that necessary if you use enough prime and your timing is right. So that idea seems like a crutch that may or may not help. You'll get your own timing down after a few bathes and then it'll be second nature, like making good BP. Did I say prime is your friend? It really is.