Last winter I built an AR with a 20" Wilson SS heavy barrel with 1:8 twist, I've finally gotten the barrel break-in completed and am ready to start working up some loads for this rifle.  It's primary function is paper-killing at 100-200 yds, and I'd like to know what bullet weight will give me optimum accuracy with the 1:8 twist.  Any good load data that's been developed would be appreciated!  I would prefer to stay with a bullet that can be magazine fed, rather than single shot.

I would experiment with the open tip match bullets and find the one that best suits your needs. Some good ones to look at include the 68 gr Hornady, 69 gr SMK, 73 gr Berger and the Hornady 75 gr. You should find excellent results with some of those. As for load data, you might want to ask around over in the reloading forum.

-Charging Handle

There is no such thing as an optimum bullet for the 1\8 twist. I know shooters using everything from 52 gr Sierra Match Kings to 77 gr Black Hills. I've shot factory match ammo in 68, 69, 75, and 77 gr from Black Hills, and Hornady 75 gr remanufactured ammo. They all gave me the same accuracy. The 69 gr Match King is the 'magic bullet' as far as AR's go. It seems to shoot well out of every rifle. The key is going to be the powder charge. You are going to find that some bullets like to run hot, and some will open up if pushed too hard. Trial and error are going to give you your 'best' load.