Buy a new Colt 6920. Semi auto, not NFA anything. Comes with the original design carrier. You fail. Please, if you don't know what you're talking about, don't post on the subject.
Also, I call BS on the arrests unless you can come up with a verified report. ATF's stance on the subject as per their letter to Colt is "We can only inform you that if this installation were to create a firearm that fires automatically, it would be a machinegun as defined; conversely, if it did not result in the production of a weapon that shoots automatically, it would be lawful to possess and make."