What's the difference between forged and cast trunions?

Both types of trunions start out as cast, and the forged ones get smashed with a big-ass anvil which aligns the microscopic structure of the steel and strengthens it while also knocking out any voids and air pockets. With cast trunions, the metal is poured into a mold and you're stuck with what you get. Forged is better than machined which is better than cast. It's reasonable to get 2,000 rounds through an AK with a cast trunion but it's mostly a luck thing. Check for cracks when you clean it.