@themanj THe buckshot barely went through, look at where the pellets hit, the pellets that went through were in most part the ones that went through the Eye opening, the ones that hit the metal part only broke the part that hit, but didn't go though, otherwise the back side of the helmet would've been destroyed by the pellets that went through the eye opening, and that didn't happen, actually the pellets barely harmed the back side of the helmet even on the buckshot. Also, Like I said, the main armor parts, like breastplate, tasset, and so on, are usually thicker than the helmet. As shown in other tests in the same guy's channel. (he tested a breastplate against all manners of crossbows, and for the most part, crossbows barely made a dent on most armors.)
"but most armors only protect vital areas ... you can shoot at their chest plate and all that lead spalling goes everywhere and much of it would hit their chin"
Uhm, nope that's actually wrong, This is actually a common misconception, battle armor, also know as full plate, actually covered almost all your body's weak spots perfectly, you could only make use of an armor's openings with a melee weapon, but it was pretty much impossible to do the same with ranged weapons. That's because of the way they were built.
You could definitely try and aim for the eye openings of a helmet though. That's what archers and musketeers would do. Most of them would fail, drop their bows and grab their secondary weapons though.
Don't worry though, only about 1-5% of all soldiers ever used such armors, that's because full plates were extremely expensive. So expensive in fact that even most nobles would think twice before buying them. THe price of one would leave even them on the red afterwards. Only Dukes and really wealthy merchants would have the money to be ok after buying one of these, I believe.