If I might be so bold, might I suggest a simpler way Baz and others. You can do it in a classroom or workshop at 28 feet - or whatever that is in old money.. The simple instructions AND a calibrated colimation chart are shown in lthe EMER AND the No4T book. Alas, the chart in the book needs to be slightly enlarged from its A5 size to the EMER Foolscap size. But it works.
After that the rifle can betaken onto the range for accuracy and zeroing. Not the same thing incidentally.
When we ttested for accuracy and zeroed, we sent the rifles out with a card attached to the paperwork to the effect that 'SNIPER RIFLE. FINAL ZEROING IS THE RESPONSIBILITY OF THE END USER'. This little attached card gave the sniper the authority to book a range (they usually shared a 400 yard range and zeroed at that for a reason I won't go into...) AND an allocation of ammunition too!
You can tell such an Armourer zeroes rifle because due to the way we did it before the sniper got his mitts on it, the amount of clicks from STOP to 16 and 16 to STOP on the azimuth/ deflection scale would be the same......, within a few. Same as the range scale. STOP to 0 and 10 to SOP, the clicks are the same.
I agree with Baz with regards to the over 500 yard/metre guide. I'd prefer to go a greater distance, known to the other teccies and refer to it as 'THE KNOWN DAP, or Distant Aiming Point
Give Tony Harveson my regards.....