Finding folks who hit that same sweet spot as C.J. Box can be tricky. His stuff isn't just 'western' in a dusty cowboy sense, it's modern, set in the contemporary Rocky Mountains with that deep respect for the land and the brutal realities of rural life. The mystery is always tight, but the setting is almost a character itself. You're looking for authors who merge outdoor procedural elements with a strong sense of place, not just historical Zane Grey-type westerns.
For a similar vibe, I'd say Craig Johnson's Walt Longmire series is the most direct comp. It's set in Wyoming, sheriff protagonist, mixes crime with the landscape beautifully. Nevada Barr's Anna Pigeon novels, though set in national parks, have that outdoor survivalist mystery angle. Paul Doiron's Mike Bowditch series (Maine game warden) is another good one—different coast, similar conflicts between man, law, and wilderness. For grittier, more noir takes with a western feel, maybe James Lee Burke's Dave Robicheaux books have that atmospheric, place-driven weight, though it's Louisiana bayou, not mountains.