Maybe I'm not looking the right place, but I'd love to find a lightweight Colt (all Colt) AR-15 rifle that has a flat top upper. Right now all I seem to find are lightweights (pencil barrel) that have the standard upper, not flat top.

I'd love to get one of the new monolothic rail Colts (they have flat tops) but I think you can only get them in M4 barrel (.750) configurations, not lightweight pencil barrels.

Any ideas or suggestions?