Так как меня, скажем так, весьма зацепила 727-я модель, решил погуглить поподробнее.
Первый вопрос, который встал - какие маркировки на ловере. АР15 сказал следующее:
Цитата:
The RO727 was never a "USGI" version.
They were marked with Colt's commercial rollmarks as "M16A2." Some late ones were also marked "M4/M16A2E." All commercial markings. Both A1 and A2 lower forgings. These commercial variants were bought "COTS," Commercial Off-The Shelf for use by specialized units that had a specific need for an M16A2 carbine variant. The M4 Carbine was being developed at the same time, and while a lot of lessons learned from one or the other probably translated back and forth - they were separate developments.
Prior to the M4 Carbine (RO920) being adopted in 1994, the last "U.S. PROP" marked USGI carbine-style ARs were XM177E2 submachine guns.
Late 80's-early 90's M-16A2 commercial roll mark

Ссылка на тему:
http://www.ar15.com/archive/topic.html?b=3&f=127&t=573855З.Ы. Небольшой пдф о планируемой замене 727 на М4А1. 2006 год кстати).
http://www.dtic.mil/ndia/2006smallarms/gaskill.pdf