Hirtius wrote on Feb 25
th, 2021 at 7:29pm:
I have found instances of Macedonian sling bullets in Thrace and some speculated lead sling bullets in Peru that are around 25 - 30 grams. I wonder what they were thinking when they made them so light? I wish there would be in-depth tests to determine how much of an effect weight has.
I strongly disagree with a light artillery assessment. As mentioned, I haven't heard of lead projectiles being used before. More importantly, the shape is biconical. That's something I've never heard of with a siege weapon before. How does firing that work? What advantage does it give? Does it tumble, and how do you stop that?
It seems more likely is that it is just what it looks like, a scaled up sling bullet. The weight, 506 grams, actually seems to line up with historical accounts of large sling stones. Sarosh made a video on slinging larger stones a while back.
https://www.youtube.com/watch?v=03tvRSuyOXkWhile the big stones obviously need to have more of a lob, I was impressed with the flight of the 450 - 500 gram stones. With lead biconicals, I'm sure it could be even better. I'm not sure how much the biconical shape helps at such a large weight, though. The larger stones he uses roughly line up with the "canoe buster" (possibly ceremonial) sling stones from some pacific islands which are over a kilogram.
The biggest surprise for me is that no one had tried this out before. I'm sure whoever made this was probably impressed with how terrifying it is, but was well aware of its impracticality in size and absurd cost.
I believe the reason why glandes were this light weight is due to a number of reasons. They were balancing economy, range, and terminal effect. Naturally they would have wanted the most effect for the cheapest possible price. We see that the later Romans generally used heavier glandes from ~50-90g which may have been because lead was cheaper and opponents became more armoured, but that is speculation.
Despite the cost, lead does make sense for a light artillery projectile. It's superior qualities would be much more noticeable in this context than something simply thrown by a sling (that is not to say it's wasn't meant for hand slinging though). Devices such as a scorpion could easily be constructed so that projectiles are launched with rifle spin, and I agree that it wouldn't be launched from something that couldn't take advantage of it's aerodynamic shape.
I love to sling stones around the 500g mark, they are very fun to throw and have great impact even over 100m. They are also quite practical in select circumstances like the 'canoe breakers' you mentioned, or close range pummeling to weaken the front lines at the beginning of a battle. This is me throwing a 590g stone 50m with my shortest, 15" sling.
https://www.youtube.com/watch?v=0Qpz8_gXCaAOr for all we know it could just be someone's wacky idea like you said. I'd like to know what caused that big gash on the reverse side of it though.