That thing looks pretty insane. What are the mods?

I've already made 1 and a half guns. Sorry, forgot to mention that. I made a small combustive myself.
(3" x 24" chamber, 2 1/2" x 30" barrel, flint spark)
And also just today actually helped my friend make a combustive (thus the 1/2) ... (4"x 24" chamber, interchangeable barrels).. shot an orange ...

Hello, all. This is my first post on here.
I have been spuddin for about a week now and am already addicted and with some research have already designed what i think will be my next gun. I figured i would post on here my designs and see what you guys think.
I am shooting for a gun that will never ...