Recently purchased a Umarex Gauntlet 2 25 cal. Which, I am really enjoying. However, not sure if I am getting the fps correct. Currently do not have a chronograph. Everything is stock, the regulator is 2100, and using JSB Match Diabolo Exact King MKII Heavy .25 Cal. Which have been working well. Wondering am I going to light or heavy. Live in the Midwest and getting cold going into winter.