Jeremy Renner -- The Gun Locker (PHOTO)

Jeremy Renner was packing some serious heat in his shopping cart Monday after a trip to a Nevada gun store.

Among the weapons Renner picked up ... a $300 Remington shotgun, a $750 Springfield Armory XD 9mm pistol and a machete. Sorry 'Avengers' fans ... no bow and arrow.

Renner's a huge gun collector ... his estranged wife made a big deal about his firearm collection in their custody war during his divorce.

The next stop ... likely Renner's 16-acre ranch outside Reno where he goes to pop off. It's not where you want to be caught trespassing.