The first CAR15 was this:
[img]http://www.softgunner.com/produkter/bilder/coltcar15.jpg[/img]
10" barrel, shortened A1 handguard and a telestock not used after this particular type of weapon.
The 10" XM177(USAF version) and 10" XM177E1(Army) followed this first one.
The final "CAR15" was the XM177E2 with a 11.5" barrel: [img]http://www.softgunner.com/produkter/bilder/coltxm177e2.jpg[/img]
The weapon used by Barnes in Platoon had a thin 16" barrel, it looks like a SP1 carbine to me.
Reasons why the XM series of carbines faded away
-In Nov. 68 Colt estimated that it would take 400 000$ and six months to complete a ballistic/kinematic study of it.
- In Dec. 68 it was recommended that the XM177E2 be reoriented to a 29month, 635 000$ R&D program, this recommedation was ignored, and the production of the "Commando" series went out.
- And in the mid 70s the BATF decided that the noise and flash suppressor was a true suppressor under tha law. And with Carter administrations decision prohibiting the export sales of suppressors, the sales of the XM177E2 received the final blow.
The above reasons are taken from The Black Rifle.