Well, a gremlin reared it's head. It started a vertical shift... I had added some weight and despite it being on the muzzle, i saw it climb. I then rezerod, but had some oddness in my clicks around 50-55yds which i couldn't lose, so went out onto the course, and promptly found a 1 moa shift. Went back to paper on the plinking range and confirmed it. So the scope has been binned and replaced with a leup comp 40x, which seems to be doing the job, holding zero through setup, plinking session and around a course.
If all this has been down to a randomly performing and then not performing scope it will be very annoying, but a lesson learned. I've tested the turrets are not slipping so it's not that, so now it will be mounted in a vice and box tested. Odd thing is that despite just a few mm difference in scope height between the two scopes (swapped mounts from low to medium), i've lost 2 MOA off each end of my trajectory.
One thing that does seem apparent and backed up with the chrono, is the first few shots on the tx, 10-20 are not at correct speed. After that though she's fine. So another lesson learned is that 3-5 shots on the plinking range before a shoot are not enough to check she's not moved. I need to do the work and put 20-30 down to prove it and not be lazy and go for a burger.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep