I have a mint, 99% only 200 rounds fired HK USP compact .40S&W pistol with three mags, HK case, manual, lock, etc. Looking for a Colt m4 stamped flattop upper receiver complete w/ 14.5" 1/7 barrel and carry handle. NO bolt and/or charging handle. I would want it unmodified with the existing birdcage flashhider not perminantly attached. Thanks!