I just built one this spring and I shoot the 180 Berger. I put a wyatts mag box in mine and I suggest you do the same. You will never touch the lands with a STW even if you shoot it single shot. Dave Kiff from Tool and Gauge said you need .180 freebore at a min with an STW or you will only get pressure spikes real fast and not get the speed you are suppose to. Mine has about .200 with the 180gr and it shoots very well. I have a 28inch Brought 9twist 5c and use 79gr of H-1000 and am pushing the 180 around 3120fps with no pressure at all. Infact I can get 5 to 6 shots out of a case easy. I am using Winchester brass do not use Remington brass it is junk.
3shots at 100
Here are two groups at 300 off the bipod. First group is 4 shots and the one that is higher then the rest is the first shot through a clean oiled bore. The next group is 3 shots and I moved the scope up a little. This rifle off the bipod at 875 yards will shoot about 7" but I cannot find my pic of some of the targets.
So do not worry about the freebore I have had 5 STW's and they all have shot great.