Most of the planes I build have checked in just over 100mph on the gun IN LEVEL FLIGHT, some a bit more depending on engine and cleanliness of airframe. I find the biggest difference comes from hitting the right prop. A couple months ago Evan Quiros Rare Bear was clocked at 138mph at Bomber Field, but he is running a BME 102 twin. We had 3 other Bearcats there all with Q75s running about 100 to 110mph.