From the Game Manual:
WILD WESTERN Taito America Corporation’s WILD WESTERN game is a journey back in time to the Wild West. You will mount your fiery steed in pursuit of a gang of bandits and feel like a real western hero when all the bandits are shot down and the locomotive safely passes through the desert.
The horses speed and direction is controlled by the 8-Way Joystick. Directional gunfire is controlled by the Revolving Control hitting the Button the player fires at the runaway bandits. The Bandits gunfire, running into cacti, rocks, or train is fatal to the player.
When a Bandit hops on the train, the player must also climb aboard in order to shoot him. Getting aboard the train requires skill and timing as he must run parallel with the train at a safe distance and push the button to get aboard. The same is true when the player returns to his horse, he must wait for his horse to run alongside the train and time his jump in order to remount his horse.
Riding the train too long is also dangerous because the player must watch for outstretched waterpipes when passing by watertanks. The player must push the button to duck under the waterpipes or be knocked from the train.
The player gets a chance to improve his aim in the bonus frame hitting the coin tossed into the air by his horse. Double the Bonus for a hit, or the horse laughs when missed.
The game ends when the player has lost all of his sheriffs or when 3 bandits have hopped aboard the train.
An additional sheriff is added for scoring 30,000 points (adjustable).