HI All, that's a tricky one for me , i have owned a really good skan chrono for years now ,so i chrono my gun now took it to a shop who also has a really good skan chrono it gave a differant reading, my mate has a new combo and it gave a differant reading ,so i went down to a friend who has just got a new caldwell ,and they all give you a differant reading ,so take your pick which one , i have my own theory on this lighting heate and position of gun when shooting, Also anyone who has a chrono get them checked with a few differant ones and i think you will be shocked. nearly forgot to say i used a daystate mk4 177cal i suply the pellets jsb exacts , atb bob.