Sooo, I gave the old girl a good scrubbing, took out a good lump of gunk out from around and under the extractor (the spring was encased in dirt), cleaned and oiled all parts that needed it.
I got two new mec-gar mags and newly fitted Nills on the grip and headed for the range once again with 100 rds (50 115gr S&B and 50 124gr Subsonic S&B).
Subsonic works fine with one round in 5 being extracted half way out of the chamber before the extractor jumped the rim. This left me with a jam since the bolt is trying to feed the next round in.
Standard 115gr I have a 1 in 5 chance of a stovepipe.
The additional problem both have in common is feeding a round in and it gets wedged half in the chamber at an angle though this was only a 1 in 10 occurrence.
All in all neither ammo offers 100% reliability yet
Suggestions most welcome.
p.s I am also learning to grip with a stiff grip since this also helps things. I am a rifle shooter by preference so it is a new experience.