What SGJ said
From the 1928 edition of “Smokeless Shotgun Powders” by Wallace Coxe, ballistic engineer of the Burnside Laboratory of the E.I. du Pont de Nemours & Co. “DuPont Oval can be loaded with 1 3/8 ounces of shot in a 12-gauge shotgun to develop the same velocity and pressure as obtained with a load of 3 1/2 drams of DuPont Bulk Smokeless Powder or 28 grains of Ballistite and 1 1/4 ounces of shot. The relation naturally holds with other charges, but as DuPont Oval is used principally for maximum loads the comparison is more striking as it shows the possibility of using a heavy load with DuPont Oval that would be an abnormal load were it used with DuPont Bulk Smokeless, Ballistite, or other existing old-style types of shotgun powders.”
Coxe reported 3 1/2 Dram Eq. 1 1/4 oz. loads (the standard c. 1900 Live Bird load):
NOTE: pressures were measured by crushers (LUP) and modern transducer measurement pressures would be 10 – 14% higher
DuPont Bulk smokeless powder - 11,700 psi
Schultze Bulk smokeless powder - 11,800 psi
28 grains of Ballistite Dense smokeless powder - 12,600 psi
Note all 3 are greater than the SAAMI 12g 2 3/4” recommended maximum pressure of 11,500 psi.
40 grains of DuPont Oval Progressive Burning powder - 9,400 psi
