DK Pistol

So I'm not sure if anyone else has found these weapons but, I've found a set of pistols "DK Pistol" that when used enlarge Rico's head and anyone that you shoot them with, they don't do any damage and have a bottomless clip, they're found on top of a roof in a corner at Vico Platessa.

Edit: http://imgur.com/a/CpCU7 link to the pictures/location of the gun.