Quote Originally Posted by SextusTheLewd
Not sure about what you meant earlier by changing the arrow weight wouldn't make a major impact on speed though. When I changed my arrows from one model to another, a difference of 40 grains roughly, my speed drops about 15fps. That's a 7% drop roughly.
I'll explain that a bit more. You see, in a firearm, when I increase bullet mass by a similar percent, I'll see a larger percentage drop in velocity. With a bow, there are mechanical issues like bowstring acceleration, etc, that are to a certain degree (more) static with regard to the arrows. Hence, compared to developing loads for a rifle, with a bow arrow weights will fall within a narrower percentage change in velocity compared to altering firearm cartridges. Basically, if I took a cartridge and changed the bullet weight by a similar percentage to what you did with your arrow while keeping the powder the same, I'd pretty likely see a larger drop in velocity.

Anyway, the issue is, the medieval bows were weapons of war. Usually in projectiles it seems that lighter and faster projectiles do more tissue damage, while heavier but slower projectiles often penetrate harder materials like wood and metal better. However, as I've said in another forum, if the tissue damage drop isn't that great, I'll lean more towards better material penetration. That was applied to the contemporary battlefield with increasing usage of body armor from all corners; but given the increasing prevalence of armor on the medieval battlefield it was likely equally valid then as well. Because if it doesn't go through the armor at all, it doesn't matter how much or little damage it can do to tissue.