I have been wanting a new inner barrel(6.03 or 6.01) to increase my KWA kmp9's performance at range. I am confused though as to what inner barrels will fit my gun(length is not a problem b/c I can cut it to size). I have looked and found the Falcon Extended Steel Precision Inner Barrel on Airsoft GI, but it seems like it is over priced, and i have heard "Installing the Falcon barrel did give me a little trouble, however, as the barrel has a very slightly larger outer diameter than the stock barrel. Because of this larger OD I was not able to properly install the REAPS bucking into the hop up. I could get everything together, but the hop up would spin the whole bucking around the barrel, and I didn't have this problem with the stock barrel and the REAPS." So if i could get a different inner barrel then cut it to size/buy the right size for cheaper I would. If any of you could give me insight as to if there is a specific type of barrel I will need that would be fantastic. Thanks in advance!