Hey Jim.
In the last ManCast (“To Frame a Marine”), you mentioned muzzle velocities on factory ammo and the “advertised” fps vs. actual fps.
About a week ago, started work on a load for my Bergara B14 Wilderness Ridge (6.5CM).
Before I started collecting data on the handload, I ran 11 rounds of Hornady American Whitetail through the rifle while running the chronograph (Garmin Xero-C1).
The factory rounds were the 128gr InterLock, which claims a muzzle velocity of 2820. (It was lot #3211343)
On the 11 rounds, I got an average of 2726.3, with a std dev of 13.3, and spread of 43.2
(For the record, my rifle does NOT like that load. One group had well over 1.5" spread.)
I have a question on how the manufacturer’s measure the velocity of a cartridge. They have a number on the box and we understand the parameters of barrel length and temp etc. But what equipment do they use to measure with? Some super expensive doppler? Also what causes the differences between Garmin and Lab Radar etc - who is right? Are the chronographs calibrated at factory somehow? I assume so as part of a production test. And if so what causes the differences between them? What is used as a known velocity controlled projectile? One or more of them are wrong.
Just wondering as an electronics engineer that has to answer questions about range of our wireless radio products - which is an almost impossible problem.