Exactly Bindi2- the british were sending teir MLE's out very poorly sighted and I just pulled my MLE out to confirm there's no way to adjust front or rear for "windage". Needless to say, the Boers had well sighted rifles. On the subject of drift we shouldn't forget about the wind. Labudda and Skennertonicon provide one example (page 13, Accurizing and shooting Lee Enfields): "fresh Wind blowing from 2 o'clock....at 600 yards.....=42 inches allowance". Totally overwhelms spin-drift and the coriolis effect. Here in Alberta with a good Chinook blowing in from the west and a WW1 sniper rifle with scope offset to the left (zeroed at 300 yards) and shooting to the north, the bullet would cross to the left of the line of sight at 300 yards, then arc out further left before being carried far back to the right by wind. The wind here is about as constant as gravity so if you shoot at a north directed range you might see consistant behavior.

Ridolpho