High Hander by William Oliver Turner

Tesno was a troubleshooter. That's why the railroad construction company had hired him. His job was to make sure that nobody interfered with the tunnel that they were digging through that frontier region mountain. Tesno knew one thing for sure--if they had called him in, there must have been plenty interference--and the kind that didn't stop at murder. Frontier towns and frontier wilderness didn't pay much attention to city-made laws. Tesno carried his own law with him and he knew he'd have to make it respected. It was the law of the six-gun and the firm high hand. Take no guff, keep your powder dry, and don't give an inch. One moment of uncertainty, and it would mean his end! - Summary by William O. Turner