Using an insert barrel has always been a compromise. Run a bored-out pump handle, let your UC kit run on the bottom edge, or bore the stock barrel and run a little loud. 
This barrel back opens up your options. By using an 8" Freak XL insert and a standard Freak front, the threads are pushed forward three inches, clearing the pump handle. Bore down over the full 8" to maximize efficiency, while running a tip of your choice for better sound signature or ergonomics. 
Coming soon - preorder now open. Insert and front not included, all photos currently show raw prototype. Finished barrel will be anodized black.