That'll ruin Your day, but luckier than it seems..

I'd have to watch it again, but that mallory(which is heavy) looked to be 2-3× the size of a 12ga. slug, Energy = mass x velocity squared, so for rough-guessing 2.5oz(.15625lb.) x 265.3 sq.'d(70,384) = 10,997 lb./ft. That's 20x a full load 357 Mag.
Std. 12ga slugs being typically 1oz. & muzzle velocity of 1350-1550 for sabots, & 1600-1760 for rifled slugs.
Yeah, You don't want to take any of these to the chest, :eek: !!!

Pounds are force, mass is in slugs (32.174 lbf = 1 slug).
2.5oz is about 0.005 slugs.
The equation for kinetic energy is 1/2mv^2.
That makes the muzzle energy about 171 ft lbf. Still not something I want to be in the way of! LOL