Yes a stone at speed smashes bone as does a musket-ball , and 1/4 , 1/3 inch steel ball . A boomerang is about 1/4 inch thick with bi-convex bullet-nose profile . Wood can't be sharpened like steel swords and wood can't have the same strength-dimensions as steel . But experts have published that wood cuts like steel. A "gash" in bone is not scientific , flesh gets gashed but bone has fractures . This appears to be an excision across cortical bone by a sword:
Kaakutja, Perhaps the First Known Boomerang Victim - The New York ...
https://www.nytimes.com/2016/10/18/science/first-boomerang-victim-australia.htmlOct 17, 2016 - The skeletal remains of Kaakutja, an aboriginal man who scientists think was killed ... A gash in the skull of Kaakutja was probably caused by a boomerang ...
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On slings , maybe a snake strikes by coiling its neck similar to sling throw. I noticed a brown snake watching my hand weeding in long grass. It kills with 2mg venom which is in 2nd place to the Inland Taipan (Oxyuranus microlepidotus) , Australia at 1.1 mg.This has the most toxic venom of any snake. Maximum yield recorded (for one bite) is 110mg. That would probably be enough to kill over 100 people or 250,000 mice.
So i swung a 10ft garden-hosepipe with a screw and lead wire on the end . The momentum was amazing and impressed the snake which stopped breathing . It beat my strike with boomerang on a forensic plastic skull which hardly dented the rubber skin but the machete mashed it.