I have read a lot of the posts in the past on this subject , but not experienced it myself,
On a similar note I have been struggling with a 21mm conversion, I can get it making the power but am dangerously close to detonation, It would shoot around 50 shots then the piston would tighten slightly and the power would go down, ( I am using an o ring skirt less design made from bronze running a tight tolerance to avoid detonation).
I decided to line the rear 75% of the piston diameter with derlin and run that % of the piston with more clearance , I lubed with very light oil (sm50), the power jumped to 12.4 ft lb, I had to remove 5mm of preload( which brought it below the point where the lube detonated),
The point is friction is very bad for springers .
All my guns bar one run small section o rings could this be the reason I don't see the temp shift problem, or have I just not experienced a high enough temperature .