When I first started casting there was an advanced group casting Zink bullets.  They were getting some incredibly high velocities with them. No lube required. I have intended to try it but never did and likely wont. I have a few hundred pounds of Zink wheel weights available if anyone is interested. 
In 22 caliber a mold that casts a 55 grain bullet will cast much lighter in Zink so can be pushed much faster and can be loaded to jacketed bullet pressures. Max velocity should be impressive but because of the poor BC of bullets cast in a low density metal will be limited in range. Anyway if anyone wants to try I have a bunch that have been sorted from lead and steel wheel weights.