I managed to get my computer running, although I'm not sure what I fixed, so next time I boot it it might be a problem again. But I managed to add some pics to the original post.
I've fired almost a brick at these plates now, and have given up using the rear bag - it's just not needed. Constantly switching between the 180m, 240m and 275m is no problem at all for the scope. I've also been using the reticle to place bullets without dialing the turret up. These three ranges are virtually impossible to miss, even kneeling with the rifle resting across the fence, unless the wind is really messing about.
Today I had a practice on those, then walked up to the other paddock, shooting off the bipod prone in the grass. I had a very difficult time getting hits at 200m though...until I realised I was at 225m! I ranged the paddock the other night to various comfortable positions from 200m out to 400m, at about 25m intervals, and noted them on paper. I wandered out and set up at where I just assumed I'd ranged 200m, dialed up 27MoA and missed the whole mag. I checked my elevation notes and realised where I was, dialed up to the calculated 33MoA, and hit the whole mag. But the hits were low on the plate, so I came up to 35MoA and fired another mag into a nice little group, although I didn't have time to go and take a shot of the plate. This plate is much larger, at 440mm high by 570mm wide and sprayed with silver galv. I wish I'd remembered to put the half-scale ram up there as well as that would've been a nice challenge.
I moved back to 250m and came up to 38.5MoA, and added 1.5MoA as I'd had to come up at 225m. I fired a mag but dropped two misses off the left edge that I called, so I was happy with that.
Then back to 300m. I dialed up 51.75MoA as calculated but they were dropping short, so I held on the 4.4MoA hold-over dot and got a hit. I dialed it up to 55MoA and got about 50% hits out of a 10rd mag. I wasn't able to see my impacts at this range though so I decided not to continue spraying bullets hopefully in the general direction. I had fairly heavy mirage at this range also, although that might be partly due to my line of sight only just passing over a crest midway to the target, and both myself and the target being on the ground, while it was quite a warm day.
I'll have to paint the target plate tomorrow and try again, and possibly take the spotting scope with me so I can see my hits