A lever-action shotgun, the M37 (actually a lever-action Shotgun rifle known as the Winchester Randall or Mare's Leg. Based off the shortened sawed off rifle used by Steve McQueen in the 1950s television show Wanted Dead or Alive ). M37 Parts A and M37 Parts B, when defeated for the fourth and fifth time, respectively. Combining the parts will make the Winchester M1892 Mare's Leg (referred to as the Western Custom in the story). This only works on the harder difficulty levels. Though it is incapable of utilizing the more powerful types of shotgun ammo, its higher rate of fire and shorter reload time make it one of the most effective weapons in the game.
In the story, the M37/1892 is featured with both the barrel and stock sawn off.