This thread saved me from going mad, thank you Neil.

I had done some tuning work on my .22 QB78DL and decided to shorten the barrel as well.

Previously this rifle had shot very respectable groups but after shortening and recrowning the barrel it was all over the place. I skimmed and recrowned three more times , and tried various different pellets, all to no avail.

Then I read this thread. I thoroughly cleaned the barrel (never, ever having been cleaned before ). I even used the brass wire brush from a Bisley cleaning kit. The filth that came out was shocking. This was followed by pull through patches treated with Youngs "303" oil (just happened to be what the gunshop had in stock).

Next I put 20 RWS Superdomes through it before trying to zero.

I could not believe the difference. Better grouping than ever.

Thanks again Neil for some superb advice.

Cheers, Mark.