New Mexico Powder Keg by J.R. Roberts

When his Darley Arabian horse, Eclipse, was stolen, Clint Adams saw red. But no sooner had he set out in pursuit of the thieves, than he found himself up to his neck in even bigger trouble. A bunch of mad revolutionaries were set on wrenching New Mexico away from the United States, and it seemed that The Gunsmith—with a little help from bounty hunter Jarred Hall—was the only man who could stop them. Before long Clint was seeing red again . . . only this time it was the stark crimson of spilled blood.