Hats off to Welshwarrior who did a really (really) nice threading and crown job for me at 5/8" x 18 UNF. Lovely undercut, thread indexes to exactly the same place each time, no funny 'kink' as the mod tightens and I still get a lovely group. Well done that man!
A note about the group...my target fell down in the closing minutes and I was due to pick someone up from the station. The pile of target, board and post did give me quite a nice aiming point....so I thought I'd see what I got. I'm happy...and Al-Croweda had better be on their toes! Cheers Daf!