The my, mentioned Sterling on powerlets:
Total 421 Joules and 363 Joules in the shoots in 235-300 fps range.
Avelerage velocity of the first 43 shoots: 249.5 fps.
Up to now it is the most efficient know Sterling... trought that the conditions of the test have not been the best - the paint was really crap and there was leak after piercing of the powerlet, up to ~ thrid shoot (I have disasembled the valve before the test, so the cup seal need "find thier proper place"...).
Details about the test conditions and the marker are here: Sterling CA efficiency tunning