I don't find that shot remarkable at all. I used to plunk ten inch rocks with regularity at about that distance with Irving, my ancient Mossy, with a select-a-choke barrel set to ever so slightly tighter than cylinder and just a bead front sight. That one ounce slug, still going at, what, 1100 f/s?, would sure make them bounce back a foot or two, if it didn't shatter them.
I sure didn't want to take a ten shot bench rest group with it, though. My shoulder would not have taken it.
Nevertheless, I can still kick myself in the butt for not buying a rifled slug barrel with front and rear sights for it for about $90.00 a couple of years ago.
Now, they're about $150.
Still wouldn't want to use more than three or four rounds to sight it in though, that's fer danged sure. Owie.
Thirty or forty years ago, when the Grasslands were still the Grasslands, and 230RN was still 230RN, it was perfectly safe to bounce one of those slugs along the ground and watch the puffs of dust progress along for what, six or seven hundred yards before the dirt-puffs got too small to discern with certainty.
Sorta like skipping rocks on a lake.
Yeah, I know, you're going to come down on me for doing such a "dangerous" thing, but it was perfectly safe back then.