The idea of Eldest Son was not to kill large numbers of the enemy but to destroy confidence in their Chinese-made arms and ammunition. After CIA ordnance techs proved it was feasible to load a 7.62x39mm round with enough high explosive to drive the bolt back into the skull of the soldier firing the weapon, the work of sabotaging thousands of rounds began. It took a month for the CIA to pry bullets from captured ammo, replace the powder with an identical-looking, HE substitute, then reseat the bullets and reseal ammo cans and crates so there was no sign of tampering. The sabotaged rounds generated up to 250,000 psi, more than five times the pressure of a normal 7.62x39mm round and enough to blow up the weapon. Several hundred 12.7 mm machine gun rounds and nearly 2000 82mm mortar rounds were booby-trapped as well, the latter being designed to explode when they hit the mortar tube's firing pin.