This isn't a days shooting, this is 10 shots and 7 of them hit the paper. What's more, it started by grouping top right then fell away down and left

I decided not to lap the barrel after derusting it, I settled instead for a few strokes with wire wool because it was looking awfully dull. I switched to "Stumpy's Moose Snot" for the patch lube and the patches are looking much better. Will give it another go with the wire wool and hopefully catch that last rough spot.

I gave it half an hour to cool while I stood in as range officer, Starting again from cold it did pretty much exactly the same thing again, two high right then falling away. I think it has to be a thermal problem.

The barrel is held in with a hooked breech and 3 wedges, the middle one is very tight, could it be bending the barrel when it tries to expand??? Getting it out won't be easy without harming the wood, but it certainly won't be tight come November :o)

I know confidence is that feeling you get just before you understand the problem, but it is looking hopeful...