The combination machine gun/shotgun that nonetheless failed to save most of Corporal Hicks' crew from being eaten and acid-splashed, has been built in real life, and legally! But alas, you can't have one.
Due to the personal time and effort it would require to produce them, even in small quantities, it would not be a good investment of resources. We have other new products to design, manufacture and sell and this project would just delay them.Dammit, don't they know that the only way to stop a bad alien with a pulse rifle is a good human with a pulse rifle? Or is it, "Guns don't kill aliens, Sigourney Weaver kills aliens"? I guess if you let her borrow your one and only copy, we're good.
Regardless, we can at least enjoy a video of the thing in action.