Heavy barrel upper

[RCS]

A few years ago, a dealer was selling three of these Colt heavy barreled uppers. The barrels are 1 in 12 twist. What model is this upper ? or is it something just put together ?

[gwp]

The HBAR 1-12 barrel configuration you have pictured with the type 2 duckbill muzzle device is the Model 606.

https://en.wikipedia.org/wiki/AR-15_variants

The Model 606 CAR-15 Heavy Assault Rifles used heavy barrels (HBAR) for sustained automatic fire. Like the Browning Automatic Rifle (BAR), the CAR-15 HBARs did not have a quick-change barrel. The HBARs could be fitted with either a Colt bipod, a M14 rifle M2 bipod, or a modified BAR bipod.

[gwp]

More Infomation:

http://pullig.dyndns.org/retroblackr...flGde/606.html

[RCS]

Thank you for the information, are these Model 606 uppers common or are they difficult to locate ?

[gwp]

CAR-15 Heavy Assault Rifle M1

I do not know how many Colt 606 were made, but the Army purchased fewer than 200 Heavy Assault Rifle M1s for use in the Small Arms Weapons Systems (SAWS) tests in 1965.

The 606 was made in several variations:

606 No forward assist

606A Forward assist

606B forward assist and four position selector (safe, semi-automatic, three-round burst, or full automatic modes)

[epa223]

Did the contour of the gas tube change on the 606's? This one appears to have the later/current bend to it.