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Quoted:
Didnt early Colt rifles use the roll pins on the FSB?
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Pun, if you are referring to the sling swivels, I think you're right. I'm pretty sure they've used rivets exclusively for the last 25-30 years though. Of course, it could have been replaced by a roll pin at any time.
I still believe that all Colt carbine barrels were marked somehow. I do know, however, that the very early 20" barrels had minimal markings compared to later barrels.
srt205, since you say the barrel finish was worn and reparked, is it possible any original markings were worn to the point of not being visible?
FWIW, the barrel looks to me be about 14.5". I base this on the position of the flats on the brake, which I assume (yah, I know) indicate the muzzle end of the barrel, and the distance between the flats and the front sight tower.
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