From West Highland Way 4: Inverarnan to Tyndrum
or the railway station, once you leave the village, the trail passes between Beinn Bheag and Beinn Odhar roughly following the railway and the A82. Heading north, the route heads directly towards Beinn Dorian which dominates the local landscape. The route follows an old military road in this area that is at times very close to the railway. Once you cross the old stone bridge over the Allt Kinglass River, the path turns towards the northwest. Here it's quite straight again as it makes it's way steadily towards Bridge of Orchy following the railway.
The grassy landscape can be quite stark with imposing Grampian Mountains on either side. There are no trees along this stretch until the Bridge of Orchy, so sunscreen is essential if you've found one of the sunny days. More likely you may experience some wind, as there is really nothing to stop the wind howling up the valley.
The Bridge of Orchy is really nothing more than a small hostel and another railway station. Here you'll cross the railway, the A82 (with caution), and the actual Bridge of Orchy over the River Orchy. This begins a somewhat difficult climb of 500 ft over 1.5 miles along the historical route of the old military road up to the Mam Carraigh summit. The first half of the climb passes through a pine wood after which the path becomes rocky and the view of the Grampian Mountains improves. From the summit, you'll have a good view of Loch Tulla with the wild, desolate, and beautiful Rannoch Moor in the background. The descent is quite rocky, with lots of loose rocks so do take care.
If you want to skip this final climb, there is a road along the River Orchy and Loch Tulla to Inveroran. Inveroran is a small hotel. From here, West Highland Way 6: Inveroran to Kings House
continues the route.