Gunsight Showdown: A Walt Slade Western, by Bradford Scott (epub/Kindle/pdf)
A RACE WITH DEATH!
The mighty bridge crossing the Rio Grande was to be the final step in the completion of the railroad and the taming of the West. But when Ranger Walt Slade saw the plans, he knew there was a sinister enemy at work -- for the bridge was being built deliberately so that it would collapse at the first flood! Tracking his hidden adversary, facing ambush, arson, and dynamite blasts, the undercover ace of the Texas Rangers fights through until he and his quarry come face to face in a Gunsight Showdown.