That has been the dispute since the day he was shot down. Allied Command gave the credit to Brown, although it was never really certain that it was a round from his Vickers machinegun, or the Vickers guns of the Australian antiaircraft unit which was also firing at Von Richtofen's plane. No ballistics tests were ever done on the fatal round, which pierced Von Richtofen's heart, and since the guns all fired the same caliber, it's anybody's guess as to who really fired the fatal shot...
the infowarrior
This show, and I understand it’s just a TV show, indicated that the round was fired from a bolt action rifle. They did all sorts of convoluted simulations to “prove” it.