The official name is the Bitterroot - Rock Creek Divide Trail, and when I looked on the maps it is also listed as the Easthouse National Recreation Trail. I have never heard anyone call it either of those. We simply call the 313.
If you don't have time for Sapphire Crest
or can't manage a shuttle on the other side at Sawmill Saddle, consider an out and back to Dome Shaped Mountain. If the descent down Big Springs
doesn't sound fun, the other option is seven more miles on 313 to Sawmill Saddle.
To begin, the trail tends to continue climbing with dramatic drop offs to your right. At 4.5 miles there is an impressive couloir descending to an unnamed lake. At 5.0 miles is the junction with Skalkaho-Gird Trail, which would eventually take you over to the Palisade Trail and Willow Creek trails. One day if we can get the resources for maintenance, it could be a fun option. For now be content to stay on 313.
The trail tops out on the top of Dome Shaped Mountain at 8650 ft and 6.6 miles. Before you get there, the trail takes a quick steep dive through some loose rock. Be careful. I got bucked off here, and from personal experience an injury here is not welcome. After the quick taste of things to come, there is more climbing as the trail becomes rocky and skirts a steep east facing bowl.
Take awhile to enjoy the views at the top and check out the Burnt Fork drainage, your eventual destination.
After topping out, the reward is mile of descending, another mile of relatively flat ridgeline, and the more downhill. At mile 10, the trail enters a recent burn, and if you are lucky the trail has been cleared, otherwise good luck. The fire burned all the lichen and moss off the granite boulders, leaving them a stark white contrasting with the surrounding blackened trees. The effect is surreal as the trail seems to weaved over and around tombstones and crypts.
Leaving the burn behind the trail begins climbing again, and a steep hike-a-bike awaits you for the last major climb up to Eagle Point. If you have any spring left in you legs, contemplate climbing the pile of scree to the top.
At this point the 313 trail has a complete change in character. It gets wider and the trail is covered with flat blocks of talus. Just remember the mantra, "Don't touch the brakes," and you'll be fine. Flat pedals don't hurt, either.