Gunsmith - The Silent Witness.

Gunsmith Josh Catlin was in London, England, when word came that his father was dead and he returned to Denver, to be told that his father Jarvis, also a gunsmith, had committed suicide. This had happened at the Cattlemen's Club, a hangout for wealthy ranchers and their associates. And as Josh probed for answers he uncovered the true motive, no suicide but murder, that these ranchers and U. S. Army personnel were involved in a plot to sell military arms to Mexico.
Josh, armed with his gunsmithing tools, set out to the ranches his father had done business with, with pieces of the puzzle coming together, to discover that instead of Mexico the ranchers were going to deliver these stolen arms to the Cuban Junta, and with orders from them to kill gunsmith Josh Catlin.