[Josh Smith]

I'm researching this right now, but it would seem that the true reason (conjecture) is the same reason the .45acp was originally chambered in 200gr instead of 230gr. Both were original chamberings.

I've always heard that 124gr (with +P pressures) was the original loading for the 9mm, but some digging may uncover more than that.

Josh <><

 

[Josh Smith]

"Ball: The earliest loads have FMJ truncated cone bullets weighing 124grains. These were replaced in Germany with 124grain FMJ bullets with a round ogive in 1915-1916 (Figure 3) though truncated cone bullets were used on commercial loads in the United States into the 1930s. Later, round nose FMJ 115 grain bullets, usually having concave bases were introduced by a number of countries including Britain (Figure 4)."

http://www.cartridgecollectors.org/intro9mm/

Josh <><