[wideawake]

The recoil from the weapon is your "equal and opposite reaction" - but you need a large caliber like a .50 or a 12-gauge slug from close range to knock someone down from the force of impact as opposed to simply putting them down from the physical trauma.

People certainly aren't sent flying backwards from being hit by a .38 round at 20 yards like they do in the movies.

[looscnnn]

I watched the episode. They used different calibers, including a shotgun (can’t remember if it was 12 or 20 gauge). The myth was not knockdown power but sending the shootee flying when they are hit by the projectile. The fact is that even with a shotgun you can not send the shootee flying.