Bill:
Average was about 60 cars a day. Newspaper accounts and discussions I have had with crews and local residents talk about trains as long as 85 cars. See the following newspaper item
August 11, 1938
Monday morning 85 cars made up the coal train going to Crested Butte.
Most Crested Butte trains were double headers from Gunnison to Crested Butte. During the 20s and 30s, and 40s, the Gunnison switcher which was 456 for years, would make the run to Crested Butte as mid-train helper to 474. After they put the K37s on the branch in 42 (they had to rebuild the bridges at Almont and East River) they did not need a helper.
The longest train ever operated on the D&RGW narrow gauge was from Sargents to Gunnison in March of 1943. The Crested Butte branch was shut down for a couple of days due to slides. After Rotary 00 opened the line, the D&RGW had accumulated a bunch of empties at Sargents and the mines at Crested Butte needed empty cars, so the D&RGW ran a train of 125 empties.