Got a great deal today on a 10.5" chrome lined upper, A2 receiver and F-marked FSB (I know that's not ideal).

Anything the military ever used SBRish with an A2 upper I could turn this thing into? I know here's the XM177 but I don't really want to hang a 5 inch flash hider on it when it can be short.

well...........the xm177 did not use an A2 upper. Assuming you would be happy with an A2 uppered 177, except for the long flash hider/moderator, then you might would also be happy with an A2 uppered 607. It used a 10 inch barrel, with the early ones using the 3 prong hider, while the later ones used a 3.5 inch moderator. (no flash hider slots)

There was the 733 used in the black hawk down timeframe that used an a2 upper on a 11.5 barrel and theres pictures of the xm177 type carbines with bird cages instead of moderators so a 10.5 with an a2 upper and birdcage would look the part just wont be a perfect clone of anything
Eta:found some pics

I know this one ^ has an a1 upper but they were made with a2s

Heh, fortunately I don't have the patience to be one of the cloners that makes every little detail match. I'd be afraid I'd get it done then not wanna beat on it too much since it's an accurate clone. Just figured I'd make something a little different but with something to model it off of.

I saw that "Blood Diamond build" thread over in the retro forum and liked it - may do something along those lines but with a regular bird cage to keep it short.