Those look like homemade, probably with a swaging die for a reloading press. People forget that RCBS stands for Rock Chuck Bullet Swage, and the Rock Chucker press got its name for being a tool to help you make bullets for shooting Rock Chucks.
The base separation doesn't seem any more likely than gas checks falling off cast bullets, but if the lead is loose in the cups, they can be pulled and a drop of Loctite put into the half-jacket before putting it back in.
The base separation doesn't seem any more likely than gas checks falling off cast bullets, but if the lead is loose in the cups, they can be pulled and a drop of Loctite put into the half-jacket before putting it back in.