necchi said:The two wrench spots are on aftermarket drums, many of the originals are all round.
I have a couple of older ones (CVAs), both with the flat spots. A Mountain rifle and a Kentucky. I hadn't noticed that at some point they changed to all round on the newer ones. Just a thinkin but maybe they changed it to make it difficult to remove on the patient breeches? I'll have to check on this more.