forgot about this for a short time !
The barrel is a Lithgowicon .. probably when it was fitted no one bothered to do a 7.62 extractor as it worked fine without it. I am not sure if it was fitted by lithgow though I suspect it may have been. Anyway, I can wonder out loud all day and it won't fix it. I will take it out and have a good look and see if I have done something wrong ( quite possible ) . If it's not ever going to fit I will put the 303 extractor back in.