get rid of it . I have a .243 with a 20" barrel . I call my self a good shot and a fair gun smith, I could not get mine to shoot better than 3" group period. I tried all the stuff on the help page and do reload but I think that the 20" barrel in .243 is just JUNK. I talk with a bunch of old gun buffs (wealth of knowledge) and they think that the rate of twist for the barrel length is too fast there fore an un stable bullet . I did slow down my reloads but this came dangerously close to below starting loads . I don't suggest that you try this, it is very dangerous. Like I said, get rid of it and save your self alot of time, money and heart ache. It will never shoot any better than a 2.5" group and you would have spent enough money to buy a Remington that will shoot 1/2" groups out the box.
GOOD LUCK
JIM