Why an ACOG? Fixed power and very, very short eye relief. No thanks.
I'd recommend a low to mid-powered variable scope w/ illuminated reticle.
IOR 1.1-4x26mmLeupold MR/T 1.5-5x20mmBurris 1-4x24mmMeopta 1-4x22mmTrijicon 1.25-4x24mmNightforce 1-4x24mmUS Optics 1-4x22mmS&B 1.1-4x20mmRegarding scope mounts,
LaRue Tactical is the only way to go if you want a repeatable zero.
Sorry arteacher, I can't endorse that Simmons of yours! Nothing personal, but HuckMeat has money to spend, why not spend it?
Regarding range, you should be able to gain proficiency out to 200+ yards in no time.
300 yards and beyond, you will begin to be limited by the low magnification of your optics and the small size of your target. Especially if it's moving.
If you're interested, I can make some scope recommendations that have a bit higher end on the magnification range.
Of course these longer ranges will require some trigger discipline, cheek weld, and stable positioning on your part.
I also looked for an article over at snipershide.com about a guy who sat in the dark at his range, comparing optics at 100 meter targets.
I couldn't find the article, but long story short, it takes some high quality glass to see in very low light.
In his article he said his US Optics and S&B could do it no problem, with his Nightforce coming in a close third.
His Leupold Mark 4 was significantly worse, not being able to see the targets clearly. I thought that was an interesting test.
Then of course if you really want to see in the dark, post your questions in the
Night Vison forum.