I would think after about three shots in a mineshaft with black powder you'd be done for quite a while because you wouldn't be able to see the target.  j

John Dutcher is probably the best source of info on CW Rowland, as he became very close with the family and has more info on Rowland than anyone I know of. He had a lot of original Rowland items, plus copies of pictures and such of other Rowland items the family didn't want to part with. I've spoken with John in Denver about Rowland, and plan to ask him some more questions in May when I see him. I better make a list, so I don't forget what I want to ask.
John  is the one who told me Rowland owned or had access to a mine shaft for testing when weather was poor. He also told me Rowland shot in his own backyard, and showed me a picture of Rowland shooting off his very sturdy bench with houses in the background. Rowland's .722" 200 yd. record group is pictured in John's Ballard book.
In an article in Outdoor Life his shooting method and preparation for the record group was described. It mentions that he cast bullets in 500 rd. groups and after sorting he usually had about 150 useable bullets. No mention of the mine shaft, so guessing since it was May he could easily shoot outdoors.
One thing that I found curious was a home made tool Rowland had in his tools that were purchased by a gentleman in Wyoming after his death in the 30's. The "tool" was a hollow wooden tube made in two halves and lined with felt. The felt was saturated with some sort of lubricant, and Rowland pushed his bullets through the tube prior to breech seating them to ensure no excess lube was outside the lube grooves. It also left a thin film of whatever lube was saturated on the felt inside the tube. I have never heard of this being done by any shooters before?