The alleged stalker of a Hollywood heavyweight faces a mountain of charges.

Joshua Corbet is sitting in jail after cops busted him allegedly creeping around a home belonging to Sandra Bullock last month.  

On top of the charges he faces for apparently breaking into the Bullock compound in West LA, prosecutors yesterday filed more charges saying he owns several illegal firearms including machine guns and assault weapons.  

Last week, Corbet pleaded not guilty to the breaking and entering charges, but if he's convicted on these new weapons charges, he could face more than 12 years in prison.