Power Stem... along time ago the military found that center ignition of a powder column created great velocity and cleaner burn.
Difference is that those US military primers and igniters for gun cartridges were filled with black powder: They were later filled with BP substitutes, including Black Mag. The 120 mm tank gun attains a velocity of over 5,000 fps without the use of a long perforated igniter. The cartridge is consumed except for a steel stub case about 4" long.