RE: Radar guns
If you just want to use the radar a few times for grins, then it's silly to spend more than $80, but if you're going to measure aircraft with any speed, you'll be disappointed. I couldn't even get the ol' Bushnell to get a reading on a 15 pound turbine until it was 50 feet away. At that distance the angle was about 30 degrees which meant a correction of almost 15%.
That's the main reason a long-range radar is worth it, as it will track the plane even when it's just a speck in the sky.
Furthermore, when measuring DS or very high speed (over 100mph) objects, the lowbuck radar only picks up the speed at the very last moment when the plane is headed absolutely direct at the user which may not be it's fastest since it's likely in or at the end of the turn the pilot must make to miss the gunner.
The acid test is: Would you let someone that you care for stand within 50 feet of a speeding object, headed directly at them?
-My two cents-