Though he put several outlaws in the Boot Hill cemetery, Breakenridge used a gun only as a last resort. But, when necessary, use it he would, in a fast and accurate manner. Before long, his skills with a gun earned him a reputation as a lethal gunfighter and few outlaws even challenged him.

He was present in Tombstone during the famous Gunfight at the O.K. Corral. He was said to have been on friendly terms with the Clanton faction, and of course, working under Johnny Behan, is generally perceived to have sided with those opposing the Earps. Many years later, when he wrote his memoirs, he would say that Wyatt Earp was a desperate character.

Though many outlaws would not challenge him, this would not be the case on March 26, 1882. The night before, two men by the names of Zwing Hunt and Billy Grounds, attempted to rob the Tombstone Mining and Milling Company in Charleston, Arizona. After being challenged, they shot and killed a man before panicking and taking off without a dime. Before long, Breakendridge deputized three men to ride with him in a posse and they began to track the two killers. Finding them at the Jack Chandler Ranch near Tombstone, a gunfight ensued. Though it lasted only seconds, when the smoke cleared, Breakenridge had killed Billy Grounds and Zwing Hunt had been wounded. Unfortunately, one of the deputized men, John Gillespie, was also dead. The other two posse members were wounded but would recover. Outlaw Zwing Hunt would also recover and escaped, but was killed by Apache Indians a short time later.

In 1888, Breakenridge changed tactics completely, accepting a position as a surveyor for Maricopa County. In this capacity, he was soon tasked with surveying the Salt River for potential dam sites. After examining several sites, he returned with a party from Phoenix in July, 1889, which included James McClintock, William J. Murphy, and John R. Norton to examine the sites Breakenridge recommended and conduct a feasibility study. Traveling on horseback it took the men a week to reach Box Canyon, near the confluence of Tonto Creek and the Salt River. Breakenridge insisted that this would be the best place for a dam and he was right. Though it would be more than a decade later before construction would start in September, 1906, Breakenridge had accurately predicted the perfect site of what is now Roosevelt Dam, completed in 1911.