The Heavy iron Cannons are weapons in the Dark of the Moon film.
The blaster was created by the Autobot Que in the Autobot NEST base. After completion, it was given to Ironhide, who greatly enjoyed the weapon, and replaced his old twin cannons with it.
Ironhide later used the blaster in the streets of Washington D.C, where he crashed into Crankcase and Crowbar while in vehicle mode. Right afterwards, he, Sideswipe, and the two Decepticons began to battle, in which Ironhide was stabbed in the chest with a spiked-boomstick - yet immediatly recovered, as he thrusted out his blaster and blasted Crowbar's face apart with it. Afterwards, he killed Crankcase, and placed his blaster on his back.
Since the Heavy Iron blaster was last seen being placed on his back, it was most likely immediately demolished (and it would've been anyway, when Ironhide completely rusted up).