I would assume the Garand sights were calibrated for the M2 load. But the 1903A3, maybe the M2, maybe the M1 load?
That's a good question because the Springfield rifle was used by many competitors at the National Matches between WW1 and WW2. I'd think that the 172-grain load would be better at long range due to the better ballistic coefficient.
I agree.
I believe the M1 172gr had a BC of about .490. The M2 150gr was about .400 BC.