Mel Gibson tank top workout arms weights Expendables

Bruce Willis who?

X17 photographers snapped Mel Gibson leaving a private gym with his trainer on Wednesday afternoon, and the 57-year-old actor showed off his buff arms in a black tank top. Seriously ... where did these lethal weapons come from?!

On Monday it was announced Gibson would join the cast of Expendables 3, and it's not like he's going to be replacing Bruce's character, but he's going to be starring opposite Sylvester Stallone and Jason Statham, so he might as well beef up for the big screen!