Lumajan

Thanks Mr. Not-Mod.

Anyway, I think a combination spring-elastic system is probably the easiest system. The spring is used to push up the last little bit of distance, while the elastic does the majority of the work. I'm pretty happy with the design of the lower part; the depth of the spring ridge is enough, and the outer bits grab onto the skewers nicely. The next version will have little flares on the end, to hold a rubber band on. The upper bit i'm not quite so happy with. I think it too should grab onto the skewers, and possibly be a little bit larger even, as to not be able to exit through the top. The top is a difficult part to design and print. The stock magazine is quite thin-walled, which makes it difficult to use the skewers. I may have to extend the print further down, so that there is a thicker bit for where the skewers attach. Which would probably increase the print cost to ~$2 for this part, but more importantly, it would take much longer. I am also considering putting the front locating nub onto the upper. There isn't really much need for it, but it sorta maybe might help.

Pictures.

Yes, because we're all in America with your quite fortunate access to tools and materials (even if it is all in imperial).

I have looked at elastic, briefly, but I think it needs more work on the riser-part that pushes discs up. Inside the magazine well it's quite tight, so putting rubber-bands up there is probably not doable very easily. Possibly a rubber band over the back of the entire gun, with a 5cm riser or so?