Personally, I think it's just another folk lore based on fear with no creditable evidence of a danger. You know like using 4f as a main charge is dangerous
Actually, a lot of BP wife tales, I've found applied once upon a time..., but don't now.
For example, the round ball "skipping over" rifling that is as fast as 1:48 or faster when using a heavy charge. Today...naw BUT..., back in the day when the grooves of the rifling were not the same width as the lands..., when they were as wide as a thick saw blade because that's what the gunsmith used to make the "cutter" when rifling the barrel... that was probably true.
Moving off of the charge? Good quality fiber wads seated firmly in a good quality steel barrel that hasn't worn from corrosion. Doubtful. BUT..., talk about a barrel from the 19th century..., a thin barrel further thinned by poor care, and some sort of slipshod, makeshift wad(s) or over-cards.... could be bad
Use a LOT of 4Fg in the same thin walled poorly maintained barrel above...., could be bad
Don't blow down the barrel..., after firing..., OK so this is silly as a warning (imho) for a person shooting alone and the gun went BOOM. Now IF you were at a shooting match with people shooting at multiple positions and a lot of smoke..., using a light target load, Yeah in the excitement and such you might not realize that your flinter or caplock only clatched or popped.....,
Beer is better for you than water. OK so THAT ONE is absolutely true
No LOL, actually when wells were not deep but ground water type..., the bacteria from the barn floor, or the freshly manured field, or your outhouse or dung heap was likely seeping into the water, so yeah, the small beer you were likely drinking was a safe water source with some B Vitamins thrown in. Low alcohol too.
LD