The next rifle I build will have an A1 upper. Hell, I never use the adjustments of the A2 upper so all of mine may as well be A1's but alas, this gives me something to wish for.
weight was a concern of mine as well when I built these three.
Poor quality photo but you might notice that the top AR is a 9mm w/t M4 prifile barrel. I liked the OLY 9mm conversion, but with the HBAR and the heavy 9mm bolt system, one had to go. So off to KKF and the barrel is now M4 profile all the way. I noticed a great decrease in weight and like it very much. It is also shortened to exactly 16 1/8" with per, attached FS as well.
Second is a Bushmaster Dissipator. What you can't see is that the barrel has been turned down to light weight configuration under the HG. Also bayo lug removed. A very good upgrade to an already great concept for an AR. I hope to one day go with an A1 upper on this one as well as the 9mm too. I don't use the A2 sights and definetly don't need elevation adjustments on a pistol cal AR!
Last(bottom) is an M4 with a cut job to be 16" as well. Three very light, very fun rifles. Don't you think?