I have an A2 upper built by Fulton Armory that incorporates a nice 1-12 twist chrome lined barrel.  I like the upper as it is very light weight, and has alway shot as well as I could with 55 grain ammunition.  I need to incorporate a telescopic sight on my rifles now so the question!  Would it be less expensive to just buy an A3 type upper?  Who sells one with a light weight barrel?  Or is there anyone who would for a reasonable price put this barrel into another upper receiver? Suggestions? Jimmy

I did that same exact thing.
I took my Colt A2 upper off and replaced it with a flat top upper.
you could do it yourself. it took me about 30 min my frst time.
I had to buy
a armorers wrench - DPMS
action block - any brand will do.
snap ring pliers

If I can do it.. anybody can. I have five thumbs on each hand.