Algodoo

Uh Oh! This gun has a very dangerous flaw (if it were a real gun). After cycling the bolt, I flipped the fire selector to "semi" and the gun started firing by itself in FULL AUTO!

By the way, have you tried making any non-firearm type of gun, such as a BB or pellet gun? There are many different types of BB gun mechanisms that range from single pump spring action, to multiple pump air guns, to CO2 guns and rifles. It might be fun for you to make some of those types of guns! What do you think?

I'll give it a shot. And I'll fix the problem

Now when I pull the bolt back, it does not go forward into battery. It seems like the spring is too weak.

Actually, the shot shell does not get pushed back fast enough to get fed to the carrier. It gets jammed halfway between the carrier and the top of the magazine

Now it works as expected. Good job!