Like the one about toggle links and " keeping my loads below a certain level so I don't stress the action".
I mean, has anyone seen a stressed action of a toggle link?
Well another one that cocks my eyebrow is using fine granulation black powder in large bores so yesterday I took my greedy girl Bess to test the theory.
Well dropping what turns out to be 67 grains of this brands 'fine' that looks like 4funder 1&1/2oz of shot works just fine but I have to plug the vent first.

Next I dropped the same charge under a wad and ball and wad.
I found a dis used " keep out" sign as a target. I figured it was the size of a small deers chest.
The first two aimed the same went low, the first nicked the bottom edge of the target, the other was two inch away. You can see the first shot just over the guns breach.
The next three I held higher and was delighted. At 30yds plus this greedy girl is deer ready on a relatively small charge of a fine grading of powder.

So there you go, myth busted.
Reproduction Besses don't blow up if you don't use course powder and I still ain't seen a ruined toggle link action !
N.