You've seen that headline and come here to ask the exact question that leapt into our minds on hearing that YouTube weapon's specialist Jerry Miculek had 'built Captain America's shield'.
"Where the hell did they find some Vibranium?!"
They didn't, okay? Vibranium isn't a thing: it's a fictional metal sitting on the same shelf as Wolverine's adamantium and Avatar's unobtainium. This shield has been built out of solid titanium, all built to the right size and weight of Captain America's iconic shield. If you're upset by that, take a moment to realise that nothing in the Marvel comics is real, and that this is all for fun. Got that? Good.
Now, watch an old guy unload a .45 hand gun into a titanium shield. It's brilliant.