Getting back to the OP,
We're getting some boots fresh out of engineer school at my unit and the more recent ones are saying that they did in fact use RCO's (ACOGs) at the rifle range on Parris Island. I went from February to May of 2010 and I used irons. Shot expert on the KD range but had 6 saved rounds on Table 2 (combat shooting) range that dropped me down to sharpshooter
When I quald with my unit for te first time it was with an ACOG and I actually shot one shot worse on the 500 but did 12 points better on table 2 and got expert.
Sgt. of Marines, 5th Award Expert Rifle, 237/250
1st Award Expert Pistol, 382/400
D Co, 4th CEB, Engineers UP!! OEF 21JUN-20SEP2011