The Devil's Advocate
Call me Dad
how about how the humans constantly fell from 600 ft drops, off sky scrapers, got in high speed accidents... and yet always landed softly... on unbreakable, unmeltable steel handstransformers age of extinction
So the tranformers are at least 20 feet tall, solid steel. So of course their weapons should logically be heavier and way bigger for the average human to handle. [example the weapons Hound uses]
But Mark Walberg easily picks up the decepticons gun, and its about the size of a M-16