This is a great image and the ending is a fine surprise. I think this reads more like prose than poetry, though, except for the fashioned ending.
I think I would give it more of a shape, sort of like crescendo in music, maybe the key would be to place you as the character and write in a mounting despair. Most of what I see here is a description of the gun itself. You've used some fine images and this is a good write, Thanks for sharing, peace,