Correct me if i'm wrong but I think I heard in a review video that the impulse barrel front will not thread on any other barrel back. Kind of a shame when KEE has the patents for the FREAK and also has the PIPE. Looks like if they were gonna take the time to make a 2-piece barrel they would've went with one of those basic platforms so we could at least get different ball sizing with it. I know this gun is down in price now but it was over 1k when it came out and without changeable backs or inserts we would have to go buy a new barrel or barrel system for this brank new 1k gun outta the box. On a side note, I think i'm gonna get me one!