Put an O-ring under the forearm. Check your scope mounting. Then shoot off bags with the bags under the pivot point of the gun. Don't shoot off the sled, too much pressure on the front of the forearm. I shoot off snowmachine seats, 4-wheeler seats, shooting sticks, or tree limbs, but I always make sure the rest is on the pivot point, not the forearm. I bust a 4" clay target at 500 yards every shot.
I use the Federal Factory duplication load. 55gr Nosler Ballistic tip, or Speer Soft Point. In front of 26gr of Winchester 748. Winchester SR primers, and Winchester brass. In fact I use this same load in all my .223s, with good results. At 100 yards I shoot clover leafs with my H&R Ultra, T/C Contender Pistol, and Carbine.