Nice job! I got all the parts. It's a pretty small game, obviously, but I like the concept.
The main thing that undermines the concept somewhat, other than the lack of combat variety, is that really you don't care about almost any of the parts you get. Because once you have a decent build, most things are downgrades. And once you have a really good build, almost everything is a downgrade.
My gun: hand cannon, rail, one in the chamber, arc, sawn-off cap, laser pointer, dash loader, last word, vampire valve and overpressure.
I ran into a bug at the end where I tried using the new boomstick ammo instead of arc, and suddenly my gun just rarely hit anything. I could not find a way to kill the last few enemies, and died.