Steve,
Check your PM.
I would strip it down and check all the seals (sp), Im thinking it's unlikey that the bolt has so much lube its hitting the reg valve with such random pressures.
Strip it down, de-grease the lot of it, check all the seals, especially the one in the barrel breach, and the ones in the reg.
Put a little grease on the bolt and on the exterior of the hollow thingy that houses the hammer spring.
Regards,
Dave