"The powder charges ranged from 47.8 gr to 49.6 gr."
Believe it or not, that may or may not be a critical factor in accuracy.
Virtually all machine made ammunition (worldwide, not just the US) has powder charges that are measured by volume, not weight. As such, the actual weight can vary depending on how the grains packed into the measure.
Julian Hatcher recounts in his one book about how a competitor at the National Matches at Camp Perry (sometime in the 1920s or 1930s) took some of the issued ammo, pulled the bullets, and weighed the charges. He was complaining bitterly about the wide variation in powder charge weights, but ignored the fact that the ammunition was helping competitors break many records that year.