Zeroing Question

[LondonEnfield]

I do things slightly differently. With factory PPU 174gr I zero so point of aim and point of impact are the same at 200yds. It then so happens that 2 clicks down gives me a bottom edge point of aim on a Fig.12 target, and 2 clicks up from the 200yds sight setting gives me a central point of aim at 300yds on the Fig 11/12. Easy peasy!

Well, until I forget that my 100yds point of aim is not centre of aiming mark and put a neat 5-round group into the top of Fritz's helmet, miles outside the 5 ring...