Where can I get a USP repaired in the states? AEX won't do it for me and I am having trouble doing it myself. Here are my problems, the band holding in the ball bearing in the hop up ripped and I need to find something to replace it. The inner barrel and outer barrel are giving me problems also fitting them, and I am having trouble with the blow back mechanism while running propane. I have a metal slide, upgraded springs and I am guessing I need to get some high flow valves to get it to run perfectly on propane right?