Anyone know the powders that were used in the two rounds circa-1920? That would address questions and limitations on pressure with the technology they had at that time.
Not absolutely sure, but "1909 Military Powder", aka Du Pont Military Rifle Powder No. 20 is what seems to be listed in Whelen's book for the 30-06.
Found one magazine reference to 47gr of No. 20 for the .30 Springfield to get 2700fps.
