The ancient Chinese crossbows were actually armor piercing and stronger than strong recurve bows - and they weren't just used during sieges. A standard (common) Han crossbow had a 387lb draw and 18-21inch powerstroke - this meant it had a power comparable to an European 1000-1200 lb winch drawn crossbow with a 7 inch powerstroke. There were several grades of Han crossbows more powerful than this.

Skallagrim did a test of a winch drawn crossbow (~1000lb draw, probably 7 inch powerstroke) with the correct armor piercing bolt was able to penetrate metal lamellar: https://www.youtube.com/watch?v=XMT6hjwY8NQ

There were some heavier Han crossbows had to be drawn with the soldier's leg muscles while they were laying on their backs.