So, all was going well at the range on Saturday, after 20 or 30 shots of the CCI std (the previous culprits) I'd had no more misfires.
I experimented with the bolt position as an engineer from Lithgow Arms had advised that if it wasn't fully down, this would cause a misfire.
Testing it slightly up (about 2 to 3mm) - shot fired ok
Slightly more out of battery (approx 5 to 6mm bolt up) and (not surprisingly) it misfired.
I only tried this on a couple of shots as it's a totally controllable variable and for the entire shoot (and I shot about 170 rounds that morning) I was very conscious to ensure the bolt was closed fully before each shot.
Since things were going ok, I decided to shoot the match that the others on the range were competing in and I switched to some SK match ammo for that.
About 8 or 9 shots in and the usual bang was replaced by the dreaded 'click'
Bugger. Problem persists...
Even though it was only one misfire, this confirms in my mind that I still have an issue and that it misfired on a different brand of ammo.
There was another club member present with a 101, so I went and asked if he'd ever had any misfires. He said he's had one or two in the year he's had his, but attributed it to dud ammo. I looked at some of his spent cases and the fp indent looked similar but very slightly harder hit than mine.
I'm now thinking it's a headspace thing, but I'll be emailing Lithgow Arms again about it for their opinion and I'll have a chat to my dealer also to get his take on where to go from here.
Scored 427/500 in the comp with loads of fliers, it seems to group 2 or 3 then it'll throw 2 fliers. Underlying issue might be related to it's accuracy.
hmm...
Will keep y'all posted