There’s so much more! These guys ran the test rifles until they literally had smooth bores.
Head on over to Lucky Gunner Labs to see the interactive barrel cutaways, close-ups of the extractors (guess what: steel-cased ammo is harder on them) and just tons of other details.
If you’re coming away from this that you should only fire premium brass-cased ammo through your guns, then you really aught to give a more thorough read. A person can still make the case for one ammo type over the other.
There’s a lot in this massive missive, worth going over a couple times, even.