Ok... a little update...
After 3 weeks of seeing no shift i took her down to South Dorset for a test before Redfearns...
Tested her at 55 and she was spot on. She seemed to be ok at 40yds as well but i was shooting a battered 40mm target, but a clean 15mm at 37.5 had me shooting 10mm or so low and so I checked the ranges.... 8,10,15 were ok, as was 55, but all else was low, worst being about 30 yds where she was off by 1 MOA. So I did the numbers again and got a good solid set. Then testing some more I saw an instant shift of 1 MOA.. instant, not gradual.... but this time on every single range, even 55. Clucking bell.
Did the numbers again and just took her to Redfearns, snagged 37 ex 49 and didn't see shift all day despite it being 5-7 degrees hotter than when I zeroed her at South Dorset. Pretty happy just to see her stay in one place for a complete shoot. I saw one 15mm go low, but that could have been me. There was a couple of 45's i saw about 10mm low as well, but nothing major. I planted most of the long ones down and it seemed when I got the wind right they fell. It was hard work with the rig not fitting me in competition mode, so there's work to be done there to get that right, which should narrow the gap between what I think she can do and what I can do with her.
Thinking back I think i've found theories as to what happened.
Taking the fore-end bolts out has solve the POI shift. Pretty certain. I think the reasons I saw further shift was because I changed pellets between my exact expresses and my old Webley Mozzies last week, and I only tested them at 55 when I did, and assumed because they were the same there that they were the same at all other ranges. I should have known better because i've seen shift between batches of exact expresses alone, let alone going back to a pellet from 8 years ago!...
The second shift I'm attributing to my 8 yd being just 2 clicks shy of the very top of my turret, and although it clicks before it stops turning, i know my other hakko scopes (i'm using a deben but have custom shops and old walther rangefinders which are pretty identical bar a few differences) actually don't move the reticule in the last 1/2-3/4 of travel on the last rotation of the turret... i'm thinking that by dialing up so far to check 8 yds, when i dial back down it's not picking up the reticule's thread at the same point and thus the zero appears to have moved.
So, i'm pretty confident she's cured and stock tension varying with humidity and temp was the cause, and taking the fore-end bolts out allows it to move without dragging the action with it. Certainly enough to continue on with her in the GP series and Germany and see what else can be done.
I'm not going to dial below 8 and just use the mildots for the moment, and i'm going to keep with these mossies for consistency, as she'll group on a screw head at 45 off the bag... hopefully with a few more shoots i'll be able to see some more consistency, and then I can weigh up getting the thing to fit me better and work out what rail slope I need. It's all very well being comfy and just dealing with stuff on the plinking range, but it's only when you get in a comp that you realise your making do's just don't cut it and there's no substitute for getting them right to start with.
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