I have a 6mm WOA, barrel from John, and I must have caught him at a time when he excepted custom work. I bought just the barrel, not an upper. My barrel has a .75" gas block, a recessed target crown, and heavier but not varmint heavy profile under the hand guard. My hand guard is a skinny M-Lok style on the upper.
I am not sure he cares, but this .8 something gas block only barrels cost him a sale when I needed a 204 Ruger barrel. I ended up ordering from Ritch, and the barrel is OK. Fit and finish were excellent, but accuracy, is still a project. I wish I could have gotten the WOA barrel, with my specs.
Squeeze