With the ACOG, you cannot quickly dial elevation settings for different ranges, you have to use the BDC settings on the reticle. These may not match the ammunition used, so do not give precise elevation settings, especially at the longer ranges.
You also can't readily dial for windage. Some CSR shooters dial for wind, some aim off.
With an ACOG, you have to concentrate on which elevation hash mark to use, and your point of aim on the target, for 10 shots against a time limit.
With other scopes, you just put the crosshair in the middle of the target and concentrate on squeezing he trigger instead.
ACOG's are great for their intended uses, where you don't know what range the next target is going to be, and may need to shoot in low light, but not the best choice for CSR.