Thanks Peter.. fear not, It won't be fired until I check a few things .. such as CHS ! It was just a thought at the time to make sure that the bolt would close and I hadn;t stuffed something up. I was not expecting to have it so tight. For the moment I won't be removing knackers, gnats or otherwise, until I can chack the headspace. If it is too tight then I won't be altering the bolt head at all. The old head was .625, the .632 was only because that's the only spare bolt head I have, not because I think it is correct. Without a CHS guage it's just guess work.
I am confdent the the extractor cutout in the barrel is only machined for a 303 style extractor amd the slightly beefier 7.62 extractor just hits the metal. When I have some $ I will get someone here with more knowledge than me to check that I am right and then fix it. In the mean time I need to find the extractor I took off the original bolt head and put it back on.