Well apparently one little washer behind the top hat and jsb 8.4s go from 660 to 760 (also removed a snug piston sleeve so that might have had effect, I should know better then to change more then one variable at a time but in a hurry to settle before we take off camping)... I’m the type that learns from doing AND studying. Not JUST studying or JUST doing when it comes to topics that I have a passion for. I’d hate to get on a forum and tell people to do this or that based off of reading then only find out that it’s incorrect, so I do like to put things into practice. Having said that... after my pelgun oil that I used, against my book lernin’, got done breaking the sound barrier over 1100fps and again dieseled at about 900fps... we settled around 760. I’ll be gone Friday Saturday and Sunday for non stop shooting so we’ll see if I did any damages from the dieseling.