Quote Originally Posted by Elthore
I think you're underestimating the amount of kinetic energy a fist sized rock will have on impact. They are dense and will have a lot more energy at a similar distance when compared with arrows.
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We don't have to estimate the energy and momentum of sling shots, arrows and bolts, we can calculate it. They have roughly the same performance. We can get the data from reconstructions of ancient and medieval weapons. A typical glandes has a weight of between 30 and 70 grams. Due to human construction and physics such a weight can not be accelerated ad infinitum with a sling. A velocity of the glandes of about 50-60 m/s is normal from a common sling. If we take 60 m/s (which is rather fast) for a glandes of 50 grams we get an E0 of 90 Joule. A typical arrow (not of a Skythic bow but of other composite or strong self bows) weights about the same and travels with about the same velocity when shot from a strong bow of perhaps 100 lbs. It is no magic that it has the same energy (and btw momentum).

Heavy arrows from strong English bows reach perhaps up to 140 Joule. Same for strong crossbow bolts. Maybe also heavy sling shots (the fist sized stone you mentioned, with far fewer range however) reached such an energy. That is however still a very low energy compared to the projectiles of muskets or modern guns. Even a medium handgun bullet has an E0 of about 500 Joule (9 mm Luger or .45 ACP). What do you think happens if you would be hit by such a handgun bullet on an aramid vest? It hurts a lot and you get a bruise, nothing more. Then imagine the impact of a glandes/stone on a linen or bronze armour... maybe the warrior would have noticed the noise (exaggerated ). And please take into account that a heavy low velocity projectile like a sling shot looses energy rather fast, and the enemy was not 0 metres away. Only the very good aerodynamic performance of arrows and glandes allow for the reaches of 200 to 300 metres.