Progress report.
I lengthened 5 cartridges to 3.075 inches and this seems to be preventing the rim lock problem although I did have to give the magazine spring a bit of a stretch to lift cartridges up properly for bolt to pick up, mainly only the 2nd round though.
A great result but strange how it was ok last time I used it with the shorter cartridges I normally use in my SHTLE Enfield. Now I know I guess.
I haven't long had the P14 and it was in very poor condition when I got it ie so dirty it wouldn't feed at all.
It is going for a birthday at a military gunsmiths which will hopefully bring it up to much better standard. My biggest problem is finding a set of wood as it has been hacked up by someone who thought they know better. At least they left the barrel alone.
Thanks for your help everyone and I will let you know how I get on with rebuild.
Cheers Mike