I use an Aimpoint T1 (mini? red dot over $250)
It is on my 12.5" 6.8 SBR. This gun plays a dual role, home defense plus short range hunting. I chose an expensive red dot (Aimpoint) because the battery life allows me to leave the optic on for YEARS at a time during home defense duty, and it's always going to function no matter how much abuse it takes in the field.
The SBR rides around on the truck console and ATV's, and is handy for quick shots inside 100 yards at moving animals, especially hogs. Anything over 100 yards, and I find that the optic is the limiting factor to precision, not rifle or shooter.