I seem to recall reading that the 7xx-series carbines produced toward the end of their run had full on "M4" feedramps.
Prior to that, they had the "extended carbine" ramps.
However I wonder if the earliest 723s and 733s, back from like the early/mid 80s, had extended ramps at all.
I do love a good 7xx-series carbine discussion. My absolute favorite Retro ARs, what with me having grown up in the 80s and 90s.
Just for the hell of it, here's this:
Apparently an XM4/RO720 with one of the barrel profile options that was
not selected.
http://i.imgur.com/FWUZlFf.jpg
To be honest, I'm not clear what the rationale behind this profile even was. At least with the familiar M4 stepped profile you understand that it was an A2/government profile barrel, but stepped to facilitate mounting of the M203.
With the profile pictured, I really don't know what they would have been going for.