Here’s how I typically do a single shot BR gun. I do it because our single shot extractors are at 11:30 and 1:30. Not your typical 3&9 so it’s very evident if the slots aren’t dead nuts. There is some drawback as the chamber mouth is easily dinged, but that can be overcome with some firing pin massaging.
The other picture is how I do 100% of the repeaters. The extractor slots are at 3 & 9 so it’s easy to just move the extractor slot cutter over to the other side of the barrel.