Don't bother for duty usage.
The Colt 6920 Trooper is hard to beat. I've seen the Trooper go for as low as $712.95 on line. I have no issue using the MagPul MBUS on a duty rifle. Look for a sale on an Aimpoint PRO. YOu're finished rifle might be a bit over $1,000.00. But you'll be close. And you'll have a Patrol Rifle that you can trust...