John Saunders 
A Colt for the Kid [EPUB ebook] 

Johnnie Callum was a half-grown boy when Donovan's riders stamped his parents' homestead flat and sent him running terrified into the night. He ran far and fast over the trackless range that was Donovan's empire and fetched up in the hands of Josh Manders, a brutal sheepherder. Manders worked him hard and in six years came near to breaking Johnnie's spirit. But not near enough. Finally, there came a day when Johnnie's resentment took charge and his big, bony hands wrapped around Manders' throat in an unshakable hold. Johnnie took Manders' horse and then worked for Sam Stevens. But when Donovan was all set up to wipe out Stevens' ranch Johnnie began to get gun-minded!