I'd love nothing more than to post a photo, but my midlenth upper is currently sitting in Denny's Shop getting re-outfitted with a GTS Midlength Recon barrel
There's lots of ACOG - fitted AR's in the picture threads though. Keep in mind though, as MattB stated above - the TR21R is more than likely rugged enough for us practicing civies, hobbyists, or paranoid disciplies of prepardness. I think the TR21 is a fantastic scope. I like the ACOG though for it's size, bombproof construction, glass quality, & Bullet Drop Compensator. I rarely shoot beyond 200 yards, but it's nice to know it's there. I have a couple CQB AR's that are set up with red dots.
If I could only have ONE AR15, it'd most likely have a TR21R, cause it's so damn versatile. Still, I think the TA31A is the best general purpose optic on the market. YMMV. With iron sights at your disposal....bucking the ACOG off the gun if I'm running CQB drills is also an option, though I'm more likely to leave it on.
The rest of the my TA31A-esque AR15 though:
DD 12.0 w/ Magpul Ladders
Phantom 5C2
Troy Industries Front and Rear BUIS
Larue ACOG Mount (thanks to CS Gunworks
)& TA31A
Stag Upper / Lower
Geissele Trigger (on order)
KNS Pins
Magpul M93B, Heavy Buffer & Strike Plate
Magpul MIAD Grip
Surefire M962C in a Larue Mount