Your trying to avoid the PDI hop up chamber? In all honestly, the stock chamber is a good design, but it's terribly executed, and most TBBs that I know of for that length are AEG cut, unless you get one custom made. I think you'll have to succumb to the PDI chamber unless you feel like waiting for EdGI or PCT to custom cut you one if they don't have any in-stock, unless other companies started to make them.