Second range test yesterday at 300m. Rifle grouped 5 rounds in about 12" from prone with sling(8" wide, 12" vertically), unsupported. Group was about 18" right, so I've made a correction on the foresight and the foresight is now all the way over one side. Didn't have a chance to shoot again after adjustment. If the rifle is now zero'd, I'll shoot some groups off some bags to better gauge accuracy.
I'll be very happy if I can get reliable 2MOA (6" at 300m) groups off the bags. I'm hoping that quite a bit of the group enlargement is due to me and my lack of regular use of standard No1Mk3 sights. Shooting off sandbags will help too.