WTS New, never used (Armalite tested), AR10A4 upper assembly (including bolt carrier assembly) with 20" chrome lined heavy barrel and recoil check. Has the addition of a black 10T fiberglass tube foregrip (Armalite installed). Purchased new: Sept 9, 2001. This barrel is not available from Armalite anymore. A new recoil check cover is included in the deal. Price $725, shipping included. Postal money order for payment.
If you want a heavy barrel for longer range then this might be the barrel for you. The extra weight provides greater stability. It's not going to be at the level of a 10T barrel, but the chrome lining makes it very reliable with easier maintenance, and it has the black barrel so it does not reflect light.
The pin that holds the brake on, looks like one flush circle about 3/16" diameter going strait up from the bottom side of the brake. There is only one spot like that so it's more like a peg. I don't remember which type of barrel that indicates.