Z- CLEAN AMMUNITION Solid ZINC Projectile, Completely Lead-Free
https://alchemistammunition.com/z-clean/ (https://alchemistammunition.com/z-clean/)
Zinc bullets. Those were all the rage back in the 60's as I recall. Everything old is new again.
Zinc is 2/3 the weight of lead. Lighter bullets that will lose velocity faster than lead. Good for short range practice. You need a good backstop that won't let the harder Zinc ricochet.