As soon as the postman knocked on my door I read thru the instructions and set it up and went to shooting for some trial and error experience. I first tried some 22s and compared rifle to pistol and noted the speed and the advertised speed on the ammo box, and the speed was really close. I then tried some .40 reloads from my G23 and noticed some interesting difference in speed between the load and the speed listed in the Lyman book. One powder load resulted in much faster speed than what the book listed and one other load with different brand powder the bullet was slower than what the book said it should be running. I had one 40 round register about 560 FPS and all the others were running around 875. As soon as the slower round registered I could tell the difference in physical feel,,,if it had not been for the numbers showing the difference I would not have noticed the light load. I loaded up several rounds and added 2 grns or powder and I could see a difference,,,that was interesting !!,,, going by felt recoil I would have not known anything different. I do have questions ,,, With my glock,,, what is the best distance from the unit for the best reading,,,or does distance make a difference. And what about where the bullet goes thru the two Vs,,,the instructions says 4" is that right or best.?? I noticed every bullet varied in speed,,is that normal ? Any tips or advice to send my way would be great !! After using this chrono I can not see how anyone loads without one,,,,it is like driving a car with a speedometer.