AR20 zero method found
A pair of 30mm adjustable mounts arrived today with weaver bases. The theory being that I'll mount the scope in the adjustables, to the existing 'over' sloped picatinny rail and adjust the front mount upwards to compensate. That saves money on a new rail at about 75 quid, gives me some extra scope height and hopefully solves the original problem I had.
Anticipated problems are - crossover! They're those mounts on threaded posts, I've had them before years ago and they're buggers to get centred. One solution I'm gonna try is to adjust the zeroing rings inside the units to the extreme of their adjustment, that should ensure both rings are aligned. It'll take the LOS about a mm off barrel centre though.
Interestingly, I bought them from a supplier in the USA, ordered on the 21st this month, they arrived today, cost including shipping...........................35 quid! I can't find anything in the UK for under 45 quid plus VAT and postage and suspect I'd still be waiting................
Although................It may yet turn out to be a false economy. I have all day tomorrow to play and see if I can the thing zeroed and not shifting, and without crossover.