“...drywall like a knife going through butter. “
Do some research, you might be surprised what it does compared to say a nine.
https://www.youtube.com/watch?v=AXOIQgfvVlE
That was interesting and surprising. All three rounds had nearly identical penetration. The .556 was stopped at panel 16 and the 00buck and 9mm were stopped at panel 15. So they all penetrated seven wall sections.
My house is admittedly not that big but I couldn’t line up more than three wall sections anywhere in it. I wish they had stated what thickness of drywall they used. It’s hard to tell from a video but it looked thicker than 1/2” which is the standard drywall used on interior walls.
I didn’t even realize it, but you beat me to the same YouTube clip.
Though useful as a direct 90 degree penetration test, a test with oblique panels and a few 2x4 studs might better illustrate the devastating power of a tumbling .556 round. As I said in my earlier comment, Once they start tumbling there’s enough inertia at that speed where you can’t predict where they will wind up. The more glancing penetration of obstacles the greater the variant.