Mech bullets were a new ordinance created by John Pope. After examining a broken mech (and accidentally blasting a hole in the wall) he noticed that the invaders projectiles have much greater penetrating power than standard bullets. He attempted to use the Alien metal from the mech's body to create a better bullet for the human resistance. Melting down the automaton's body and manufacturing .45 caliber bullets.
He demonstrates their effectiveness to the second Mass who make it their standard ammunition ordering Pope to go into mass production on the weapon for their counter-offensive against the Tower in Boston.
- The weapon was rolled out for every caliber bullet, not just .45 rounds. Various machine gun ammunition and RPG shells were coated with mech metal to increase their effectiveness for the assault on the tower at the end of season one.
- The advantage was quietly abandoned for season 2 explained by one of the series producers as "they no longer have the hardware or the ability to create these mech bullets" in reality he simply disliked the idea of "magic bullets."