A newbie  to doing the retros but, been playing w/t SOPMOD clones. I put together a SOPMOD Block I and II, sold the Block II upper off and still have my Block I. I am looking forward to doing a  723 with A2 profile barrel and M203 cut upper as soon as my parts come in. It won't be a perfect clone since it's a 14.5 pinned to 16 and I'll most likely pin it onto my modern Colt M4 carbine lower for now.

         Anyway, Hello!

            Fastfoot

Welcome to "Retro", brother.   I did just the opposite of you, as I started out building retros, and then stepped over to CQBR block II.   Retros are a different kind of build process as so many of the sought after parts just don't exist in any number.  New/modern cloning is basically a matter of money. You decide what you want and order the parts. Retros can require weeks/months/years of searching for that one or two, or three particular parts.
 So, I've done old old and new/modern, but am not too familier with the 700 series builds. What's build sheet look like for a 723, or did you say 727.   I have an 11 1/2" Colt barrel, which I think has a 2000 date on it. Wasn't it a 723/727 barrel?   Believe it's .625 frt sight base diameter.

dbl tap.....grrrr

Here are two 723s I did.

Early model ( I went with a 14.7" barrel and a permanent A2 FH)





Later Model (14.5" Colt M203 profile barrel and a permanent A2 FH w/ jam nut)

I love 604's as rifles... but for carbines those are perfection.  Even better is an Israeli menusar barrel with those same setups.

     jrs93accord pretty much nailed it w/t later 723.  My Colt  A1/C7 arrived today from Bill in Or. and it looks great! It's been refinished in black instead of the  Colt Sporter grey. Now just waiting on the Colt 14.5 barrel assembly.

    I have a Colt CAR stock in hand and a Colt  BCG ready for the build.  Thinking about a Colt A1 grip for the modern M4 carbine lower and then tracking down a set of 6 hole skinny hand guards.

      Fastfoot