Zuni Gold (Gatling Western #1‪)‬

Gatling was a master armorer, a dead shot and an expert in his field—which was death. Armed with the latest automatic weapons from all over the world and paid in gold to test them on living bodies, he was probably the single most dangerous man in the Old West. At his command he had more firepower than a cavalry regiment, and more guts than a Cheyenne war party. He would need all of his skill to take on...
THE MISSION
The Copper Trust was arming the savage Jicarilla Apaches to drive the peaceful Zunis off their land. A mountain of ore was at stake and the Zunis had only one weapon—Gatling. The odds were a hundred to one against him, but Gatling figured it was the Apaches who had better start praying.