Why certain grain bullets

[jwagess]

For example 124 gr 9mm? Why not round it to 125 gr? What processs is involved in selecting a particular grain of bullet?

[JohnKSa]

Who says that the guy who designed the 9mm was measuring bullet weight in grains? Maybe he was using grams as a weight measurement.

[Merkavaboy]

Actually the original 9x19mm cartridge as designed by Georg Luger and loaded by Deutsche Waffen und Munitionsfabriken (headstamped: DWM K 480C K) was loaded with an 8 gram (123 grain) truncated cone flat point bullet (designated 278F). This was the loading that was used in the Thompson-LeGarde tests in 1904.