Gun

Gun cheat codes: 
Bonuses:
Successfully complete story mode to unlock Reed's armored horse,
Magruder's seven barrel Nock gun, and the Cannon Nock gun.

Successfully complete Pony Express to unlock silver spurs.

Successfully complete Hunting to unlock the Apache shirt.

Unlimited ammunition:
Take a barrel of TNT from the Badlands mine. Find the abandoned
house in the Badlands where the buffalo graze. Go to the back of
the house on the outside. Face the chimney (looking west) and
place the TNT barrel on the left side of the chimney. Blow up
the TNT barrel to open a hole in the ground with unlimited ammunition
for all weapons.