Interesting Colt heavy barrel

[GUTS]

Jeff, I was able to check this early upper and heavy barrel over this weekend. The upper has the Colt triangle and square C in front of the ejection port, no FW or brass deflector. The ejection port cover looks just like the 604. The slip ring is flat. The rear sight drum has only an arrow R.

The barrel is .680 at the muzzle, .715 in front of the front sight base and .750 between the bayonet lug and swivel. I checked the barrel again, it is 1X12 twist. The barrel has the exact profile as your photo of the Model 606 profile. The handguards are the glossy black triangular.

I have plans to get this upper/heavy barrel back as I think it is kind of a rare item. Thanks for your help and posting the photo of the 606 barrel profile

Does the upper look like this, no numbers on the sight wheel, just an arrow R and no arrow on the reciever itself?

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[RCS]

The upper looks like your photo except the sight wheel is smooth - with the R than arrow. The upper has a raised I arrow R to the upper right of the sight wheel. The Colt triangle is above the C in box same location. The flat part of the peep sight has 0 1 u stamped on it

[GUTS]

It sounds like a 604 upper, which is correct for the 606. Is it rounded or straight right here:

[RCS]

The upper looks just like your photo. When I see this upper again, I will try and get a photo. My question, are these 606 heavy barreled uppers around ? and what is an approx fair value as it has the 1 in 12 twist.

[RCS]

Attachment 19646Attachment 19647Attachment 19648Attachment 19649Attachment 19650Here are some additional photos of this Colt upper with 1x12 twist heavy barrel stamped CMP B. Photos show the barrel profile and inside the handguards.