I'm looking at buying a new Crown MKII in .22cal with the 500mm liner. Does this one shoot the 18gr and 25gr JSB pellets equally as well, or does it prefer one over the other? Is it possible to have a tune that is around 500fps on the bottom end that is still accurate? I would normally shoot it in the 850-900fps range, but I may need a quiet and less powerful setting in certain situations. Would I be able to adjust the power wheel and transfer port to achieve this without touching the reg?