Distance: 4.8 km (8.0 DOC hours) - Unmarked route, hard
Altitude: 1614m to 2558m. Gain: 327m. Loss: 975m . Gradient: 16 deg
Skills: Snow / ice (5/7)

Unmarked route, hard (8/9)
Unmarked route, no clear geographic features to follow

Secondary, unmapped (4/5)
Route not on maps, an alternative recognised access to hut or along range / catchment

Unknown (difficulty: 0/5)
Not specified

Unknown (difficulty: 0/5)
Not specified

Snow / ice (difficulty: 5/7)
Scramble with snow/ice sections, ice axe & crampons required

Unknown (difficulty: 0/6)
Not specified

Unknown (difficulty: 0/7)
Not specified

No description

Note: Described in the reverse direction to your journey

Ascend stream directly to Shepherds Pass. Scramble up unlikely-looking ledges in a zigzag fashion on the west side of the ridge in the direction of O'Leary Peak to reach to ridge 100m or so above the pass. Ascend easy scree/snow to Luncheon Col. O'Leary Peak easy scree/snow to summit.
Descend Luncheon Col, we did not take the best route and descended almost directly, this involved steep downclimbing (belayed) just above and crossing the shrund to the Birley Glacier proper. The better route (as we saw from below and as marked on the topo) would be to traverse/descend SW before cutting back in an SE direction down a broader spur to reach the glacier proper.
Easy travel across Wright Col to the Biv.