Impressive shooting indeed...kind of hard to figure the drop unless we have more input on the Brit ammo...
A friend who is really into this stuff advised me to sight in 2" high at 100 yards for my Ruger M77 in 7mm Rem. Mag. caliber...he said this would put me in kill shot area out to 250 yards or so...
He also said 7mm, .28 caliber "flies well"...meaning a good ballistic coefficient, better than .30 caliber. This helped me pick 7mm Rem. Mag. over 300 Winchester Mag. as an elk hunting round...
I wasn't too interested in knowing much beyond that...I sighted in using Norma brand 160 grain ammo...boat-tail bullet. It works...