NFL Star Brandon Jacobs -- My 1st Action Movie ... With Fight Scenes & Gun Battle!!

Vernon Davis ain't the only NFL star trying to make the jump to the big screen -- former NY Giants running back Brandon Jacobs just shot his 1st movie ... complete with a real FIGHT SCENE!!

The project is called "The Grievance Group" -- in which Jacobs plays the leader of a militant army trying to protect his community.

He's pretty bad ass ... he yells at a bunch of people, fights a guy in army fatigues and (pretends) to fire a heavy duty machine gun.

We spoke with the film's director Rob Hawk who tells us they started shooting the flick about 7 months ago in New Jersey -- and he's almost finished with production.

Hawk says the movie will open in 20 theaters on the East Coast in September and hopes it expands from there.

As for Brandon, we're told he's got a real interest in acting -- and hopes this role can springboard his acting career.