I've tried for several years to identify an AR-15 I have, but to no avail. It is a Colt pre-ban.
It looks like a Model 6520, but with an A1 sight.
It has the flat sided mag well, CAR-15, marked AR-15 A2, Sporter II, CAL .223, serial # SP 31XXXX.
Like I said, it's marked A2, but has the A1 rear sight. This is the way it came from the factory, no one has changed or modified it.
It's barrel is marked "C MP 5.56 NATO 1/7", so it has the 1/7" twist. It also has the teardrop forward assist.
Does anyone know what model it is?

Thanks.

Thanks, I'll post over there.

brouhaha,

My lower is identical to yours, but, of course, my upper is a CAR configuration, with forward assist.
I've had this rifle for over 10 or 11 years and was unshot when I received it. Paid $600, man I wish I had bought twenty of them.
I might call Colt and see if they can identify it. Knowing Colt, they will probably want some money to do the research.
Thanks for your help!

I've found out my AR is a model 6420. A transitional model, built between '85 and '87.
Although a 6420 has the later style birdcage flashhider, mine came with the early style.

HTH some of the others out there and thanks for your input.