At best I think 'notching' a barrel chamber is silly!
Never heard of that before.
Alledgedly back in the day Custer was getting his azz kicked and command wiped out, the ammo the army used in 1876 might indeed jam or get stuck in their guns. But that was 15 decades ago and ammo nowadays is much better!
If on the other hand you were using a chamber adapter (this idea crossed my mind when I opened this thread), marking a chamber mouth might be okay if you were indexing the adapter with whatever barrel you might have.