radar signal return
Amount of signal return has no bearing on reading. Either you get a reading or you dont. It works on doppler shift. A semi or a BB produces the same shift for the same speed. If it picks up a signal its going to give the correct reading.
Have you ever been a timer at a sporting event? Three people in the same lane will have different times that are several tenths of a second different apart. Error is from starting and stopping watches. Timing an event by hand under two seconds 500 feet apart is inherantly very inaccurate and imprecise.
10 years makes a huge difference. My gun is better than the state of the art gun 10 years back. Look at computers or any other device you wish. The principle is sound and the implimentation is now remarkable. Take a gun when you have those watches going and you will easily see how anything that involves human input is not going to be nearly as good as an electronic device.