How do you calibrate a chronograph to give "accurate" velocity readings? I have never seen calibration rounds for sale, and the only known standard I have is way too fast (3E10 cm/second) to calibrate with. Besides, a photon won't trip the sky screens and it's too hard to capture a single photon.

Do you guys just use a commercially manufactured round, shoot several times and correct for SD, Extreme Spread, etc? I have found way too much commercial ammo is optimistic in its stated velocity, and the same holds for my reloading manuals. Or am I looking for perfection when a "my loads are as fast as commercial stuff" is all I really need.

My scale weights, my calipers and micrometers are traceable to NIST Standards, but I can't find any way to do the same for my chronograph.