The singletrack portion of this ride is on the 515
trail in the Lassen National Forest, which runs from the headwaters of Butte Creek to Jonesville. The rest is on Forest Road. The road is basically to avoid ascending the trail, as that is much more difficult than coming down.
The payoff of this route is the view and proximity to Butte Creek all along the way. Also, a stop at the Butte Creek House Meadow is recommended, as it is the headwaters of a spring-run salmon population (mostly brook trout here though, salmon got stopped way below).
All three eateries in Butte Meadows are good mountain bar/cafes.
As shown, this loop starts with the downhill 515
singletrack along the creek, and finishes with a road climb and small road descent. If you come from the Paradise or Philbrook side, do the loop as shown. There is a small, marked parking area at the top end just west of the bridge at Butte Creek House Meadows.
If you came up the hill from Chico via Hwy 32 to Butte Meadow, you'll start the trail midway with a road climb and end with singletrack. Continue past Butte Meadows on the paved road to park in the Jonesville SnoPark. Ride up a stretch of pavement past the historic Jonesville Hotel. The road turns to dirt, and then at the Y, veer right, slightly downhill.
Stay on that road (26N27) for several miles gradually climbing to a large intersection with Humbug Summit Rd. Go right down the hill on road 27N11 toward Butte Creek and a bridge. West of the bridge, watch for a tiny pull-off area, and the 515
sign post (its not labeled at the road) and trail.
At the bottom end of the trail, you cross an abandoned log landing, and pick up the trail on the other side of it. It goes another 1/4 mile, then spits you out onto Mickey Trail road. Only one way out - downhill, onto Jones Creek Road, and finally a left back onto the main road leading to the SnoPark.