Nate-Lab, I agree with Quackshot and I too have killed pds at 475 yards with it's first cousin, the 20 TAC(driver). Use the 39 gr. Sierras and you can drive it to 3800fps easily and very accurately! I've got a 223 and a 223A.I. and the 20 TAC. In an AR platform they rule in a PD town! Oh, and while they kill at 500, it ain't pretty. Not much energy at that range. You'll be pleasantly surprised at how much fun it is, accurate, hard hitting, and low noise and recoil. As to triggers, I have tried a lot of them. For my money, it's the Geissele SSA-E. Yeah, it's more than a Rock River Match, which is great, but the Geissele is better, IMHO.
If you're going to have one built, go for a 26 inch cut rifled barrel of medium wt. It will give you the accuracy and you can see impacts !!!