75/80/88g ELDMs are going to be your best bet. They fly far and flat out kill stuff...
I'm over in Hermiston and also have couple private ranges, thousands of private acres at my disposal, and one range is a 1400 yarder with steel from 300-1400 every 100 yards.
I just built myself a LR 223 trainer designed around the 75/80g ELDMs, custom throated for a COAL of 2.510" Early 70s Rem 700, 28" HV Bartlein 8 twist, Greyboe Renegade M5, Timney set at 1.5#, Leupold MK4 20 MOA base, MK4 rings, MK4 6.5-20X. I shoot the 75g ELDMs at 3050fps with H4895 into 1/4-3/8 MOA and run it out to 1200 easily. Rifle weighs 15# and compliments my 6mm Creed and 7-300 Win Mag that are both set up almost exactly the same, except they both have McMillan A5s and Bartlein Rem Varmint contours. They also weigh 15-16#
223 Wylde