Major Sir Gerald Burrard, The Modern Shotgun, Volume II, The Cartridge, 1955 3rd Revised Edition pressures converted from Long Tons/ Sq. Inch (no 10-14% addition)
................................Standard service pressure - Maximum service pressures
16g 2 1/2 7/8 oz. 2 1/2 Dr. Eq. - 8,624 psi - 11,312 psi
16g 2 3/4 1 oz. 2 7/8 Dr. Eq. - 9,296 psi - 11,984 psi