Update; the problem was the scope. I've fitted a butthook and a nice Deben and have been on a really hot streak the last couple of months. Managed to win FFTA winter league and the association championships [with a performance I was most proud of, 36 ex 40 on a very hard course in horrible conditions, won by 4, not done that for a while]. Zero has been almost totally solid since putting the Deben on and the pure accuracy still impresses me greatly. Weight has been to my advantage in the gusty conditions this winter; I'm sure it's been more stable than a lighter gun. I'm not really having to think about the machinery anymore.....Really enjoying working on my shooting rather that messing about with equipment all the time.