Bret Devereaux

Who's "They" in that sentence? plate? I don't disagree on plate! Only debating mail. See @BretDevereaux 's blog post on historical archery, which does a very nice job on plate, mail, and the energy of bows. (he'll chime in with link)

For me, the two biggest unanswered questions when it comes to arrows/bolts vs. mail is the impact of angle-of-attack and of movement. AoA effect against plate can be calculated fairly easily, mail is much more complex and I haven't seen tests w/ high AoA.

Meanwhile, it seems plausible, but untested, that a body's movement might also make splitting the rings harder, as the mail shifts (e.g. w/ a person running). I have my doubts on this, but worth testing.

Note that when testing armor penetration, the biggest thing is that it is not a yes/no, but a probability cloud. Plate varies greatly in thickness even within a single suit, often from >1mm to 2+mm within single armors. Plus angle-of-attack makes a huge difference.