Like @SmashTheState said, hydrostatic shock is often what causes the bulk of a bullet’s damage. This is particularly true for flatter nosed bullets and hollow-points, which expand after entry and slow down after the force has been dispersed. Rifle rounds normally to go right through and actually cause less damage (but hollow point and similar types of rounds exist for rifles). Shotguns tend to use a number of smaller projectiles, which are usually round and therefore disperse their force, causing a lot of damage (particularly when there’s a dozen or more of them).
And like @Nullo mentioned, most modern firearms propel projectiles with a lot of force, often enough to pass through (though it’s not actually because of the propellent’s inherent force, which is actually less than the black powder used in old firearms, but rather the fact that the force builds up more behind to bullet). However, if that force is spread throughout the body by the hydrostatic shock, it can do tons of damage.
So it depends on if it’s a round designed to pierce and cause bleeding, or one intended to cause a lot of internal damage. Basically, if it’s anything but small caliber rounds or full metal rifle rounds, I don’t give even a bodybuilder much chance, since most other rounds would probably obliterate several organs with any sort of abdominal shot.