Retained energy - .22 vs .177

[GPConway]

I have found his values to be near what is stated in Chirgun but I find the Chiargun values closer to the POIs that I get with my rifles.Although I must say that ambient temperature does make a lot of difference.

A.G

... and the ambient pressure even more so since air density is proportional to absolute pressure/absolute temperature.
The average altitude in the UK is 531 Ft and in the USA: 2493 Ft. according to Wikipedia.
If the ambient pressure isn't measured explicitly at the time of testing then those average altitudes correspond to average errors in measured BC of ~2% and ~9% respectively before the effects of ambient temperature, relative humidity and equipment accuracy/repeatability are considered. Do these tests on a hot summer day in Colorado (or a mid-winter day in Norwich) without all of the necessary compensations and the calculated BC values could easily be 25% or more in error.

George