When I was staioned at Carson, I always went out to dragonman's. Out east of town along Hwy 94, not even 20 minutes from post if traffic was good. I do not remember how long the range is, 200 yards iirc. But you can always rent a Thompson or a M2 while you are out there if you feel like throwing money down range. Pulled this info off the net, the address is good, but not sure about the phone#.
1225 Dragonman Dr.
Colorado Springs, Colorado 80929
If you are looking for true long range stuff, and an actually range with facilities, I think there is one NE of Denver, but requires a membership, and then there is the big one down in Raton, NM. Hope this all helped some.
Dulce et decorum est pro patria mori