Yep, sent it back dirty, full of brass shavings, with about a dozen variably damaged empty casings. Sent them an email with specifics, and a link to the video, too.Well, hopefully you sent it back again dirty, lousy with all the brass shavings still in place.
If you were looking for a defensive use weapon, I would say an AR is fine, but not in 300blk. Your testing and seeing the wide variety of power levels, and functional differences in commercial ammo is pretty much all I should have to say on that subject. Soft Point 5.56/223 is plenty capable while dropping in lethality by A LOT after just 2 layers of drywall.
But, that's hindsight stuff at this point, hopefully your pistol gets sorted out quickly.
When I say "ideal defensive weapon" I really mean ideal for my situation. My dominant hand was recently injured, and I'm having a hard time shooting traditional pistols. So I wanted a gun I can shoot like a rifle, carry loaded in my truck, or on my person if need be, wield in tight spaces, not throw blinding fireballs, and not blow my ears out. I can't carry a loaded rifle in NH. I wouldn't want to run 5.56 in a sub 10" barrel. So 300blk fit the bill since it'll achieve design performance in 8 inches, 45ACP ballistics (saving my hearing/awareness) for indoor use, or reach out 300 yards/drop a bear with a mag change.