One theory...
It may still be burning off excess oil? If there is an excess of oil in the tube when you shoot it, you use up the excess oil in the compression tube area swept by the piston seal, but not behind it. Leave the gun sit for awhile, and more oil will have time to creap forward (yes, oil will spread uphill) from where the seal doesn't sweep the tube, to where it does. The differances in POI may have to do with differances in sitting time intervals and room temperature changes, both of which affect how much the oil would spread in the tube
??
Again, it's just a theory, but my gun did that before I cleaned out the oil.
Before that, when I'd shoot enough, the gun would smoke less, so I assume that I had shot up some of the excess oil that had spread to swept area of the compression chamber. Once I saw the smoke level thinning out in the barrel, I noticed the groups would start to tighten up some also. Then the groups would settle down to a certain size which I suspect was then only due to the inconsistancy of having a bad seal.
Cleaning out the gun and replacing the bad seal eliminated those two-stage poor groups.
Paul.
