That looks awesome! It should probably have the barrels arranged two over one, though, in keeping with the dual drum/cylinder design (assuming the outer drum/cylinder holds twice as many shells as the inner one).
no clue! lol. i was about 17 when i made this and had no idea how guns even worked. i just like the aesthetic aspects of weapons. i am mentally more intrigued with form rather than function. one of my downfalls.
so no clue why it has rifled barrels. just knew it looked good