I can't answer for John Burns, but I've killed a number of animals at less than 100 yards with VLD's, and have seen several other people do it. The bullets ranged from 115-grain .25's to 185-grain .30's, with several others in between, and the shortest range was 18 yards.

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck