A number of years back, I acquired a small number of barrels from a liquidator. As best I could tell, these were Colt barrels, or perhaps outsourced to a barrel maker for Colt to make one of their AR Match rifles. I forget the model number, but 5 or more years back, Colt sold a number of different rifles as "AR15 Match Target, AR15 HBAR match," and so forth. I forget the exact titles, but some had FSB, and others did not. They had SS barrels without threads, and 20" and 24" variants, in the black and in the white, with target crowns. Some had M16 style hand guards, and others had a free-floating tube.
Anyway, I have some of these barrels, but the only marking is a "G" at the base, near the extension. It looks like a 1:9 twist, and current has not gas port drilled, but that is another story.
My question is: Does anyone know what the "G" mark is for? It has no Colt markings. My guess is that these were outsourced, as Colt barrels are typically (always ?) phosphated chrome lined Chrome-Moly steel, and when Colt discontinued their target match line, the barrel maker was stuck with barrels and no buyer.