Seriously, a bullet would have cracked it around the impact site. It also wouldn't be perfectly round. I thought these types overlapped a lot with gun nuts. Why the hell isn't this being called out?
A French, a German, and a Russian archeologist all got together to compare their findings.
The French archeologist went first. "We dug down one hundred feet and found bits of copper," he declared, "and from this we have concluded that a thousand years ago France had internet via telephone wire!"
"That is nothing!" exclaimed the German. "In Germany, we dug down two hundred feet and found bits of glass, and from this we have concluded that two thousand years ago Germans had fiber-optic internet!"
"You are both charlatans!" bellowed the Russian, "And what's more your cultures are inferior! Behold! We Russians dug down three hundred feet and discovered absolutely nothing, and from this we can conclusively prove that three thousand years ago Russia had WiFi!"
Eh, it's a Facebook group. The only people seeing it are likely ones that are looking for any excuse to feel the numinous in the mundane. They're chasing a sense of being among the cognoscenti, of being in on a great secret. Poking holes in the "mystery" doesn't allow that.
Gun nuts tend to not be too into the whole ufo/cryptid type of obsession, at least not that I've run into online or at gun stores. Definitely haven't at the range, but I only shoot at the range with either the left wing crazies (like myself), or the area LGBTQ+ club when they want an extra hand doing tips and general safety observers.
But there is some overlap, particularly among the general conspiracy theory crowds that dabble in the ufo/cryptid stuff as well. Those folks tend to be preppers as well, which ends up matching well with gun nuts (as opposed to perfectly sane and non-obsessive firearm enthusiasts), and once those overlap, you can essentially guarantee they're right wing, and there's a high probability they'll be on the white supremacy and/or christo-fascist bandwagon too.
The Venn diagram of this would look like a Rorschach blot.
Now I'm not saying it this is what caused that hole to be there, but I wonder if these people realize that the term bullet originated with sling weaponry.