I have checked out the bolt. The bolt handle is numbered to the receiver. It has a #2 head which I unscrewed and eximained. The fireing pin I cannot remove as I do not have the correct tool, but it appears to be ok. There was oil but no cosmoline and the bolt head appeared to be clean.
All other screws are tight!
I have not had the opptuneity to go back to the range again, but hope to this weekend.
If it happens again I will have to have the rifle checked again I guess! :?