Rick , front line use was almost all limited to the M1903 / A1 . The old units ( first in the fight ) had M1903s , Grenade launching was M1903s ( better rear sight set up for that ) , etc.
There are a few exceptions , but most A3s were given to support units . Of course , engineers , truck drivers , artillery units , MPs , etc. could find themselves on or behind the front lines at any time.
Still , it did serve . There are pics of a few front line units armed with these and shots of individuals that might have been from an aux. unit or just might have preffered it .
Chris