Yes - In order to receive the unlimited ammo weapons, you must use the Store from the main game menu and purchase both the Dragoon AND the Unlimited Ammo.
THEN you have to play the game until you meet The Duke and he will sell you the Dragoon. You have to play through the first part of the game to use these weapons, but at least you dont actually have to fight any real enemies aside from the few lycans in the beginning and then surviving the lycan attack.
Good LUCK!