15fpe - I have not seen mention of cailbre - ie: 4.5mm or 5.5mm?

Normal pellet in .22 (5.5) will run 620fps to 660fps depending on pellet weight. Pellets above 18gr. will have to be moving even slower.

In .177, over 850 to 900fps will work at that power limit depending on pellet weight. 900fps (14.75fpe) makes for a really flat trajectory over 60yards with an 8.2gr. pellet.