Dang it I just erased my post trying to post a link so let me try again. As was stated by another poster I really don't see much use for this. Mr. Canterbury likes to adopt some of the old 18th century Longhunter ways to today. In a lot of ways this makes sense as there was a lot of old tricks and techniques that are still viable in todays world. He collaborated with short lane arms which make shotgun adapters who brought out a 209 shotgun adapter. Now one doesn't have to cut the brass off a spent hull to do this. Just pay attention to the particulars in his firearms videos and don't take anything he says as gospel. He mentioned in one video that the rifling on slugs are there to impart spin and stabalize the slug as it travels in the atmosphere
Hard to believe that a expert (so called) actually said that because some folks that aren't very knowledgeable wil believe him. While that is but one small example he could be putting out some really bad info that could be dangerous.
Another reason that he mentioned the use of Black powder in the 12GA was due to the ammo shortage, so this way you would still ba able to hunt. However I never noticed a shortage of shotshell ammo during the great shortage, and if there were I would reload my own with smokeless well before using Black powder. The most useful video he did IMHO is showing how to modify brass shotshells to accept 209 primers.
As much as he tries to emulate the longhunters I find it interesting that he professes the use of the 12GA since longhunters actually used 20GA French fusil de chase fowlers. The 20GA will net the user with the same results as the 12GA and more. What the 20GA offers is more shots since it uses less powder and lead as does the 12GA. In a long term situation which he does mention quite a bit this is a huge benefit the 20GA has over the 12GA. For my own knowledge I wanted to see how many 20GA shells would fit in a empty 12GA box. I found that I could fit 36 20GA shells in a 12GA box, 44% more ammo in the same space that 25 12GA shells take up. When loading black powder I'm not sure you would get that much more out of the 20GA but I know you would still get more shots out of a pound of powder and shot than you would if using a 12GA.
On his channel there is a two part Advanced Scout documentary where he fashions the class after a longhunters camp and the students must bring in a set amount of game to attain his advanced scout rating. His requirement to his students is they bring a shotgun with 1 pound of shot and Black powder (or equivalent) or 10 preloaded shells with Black powder. I would love to know why he won't allow modern smokeless ammo and only 10 pre loaded Black powder shells.