PG-13 has become an essentially meaningless rating:

...a new study indicates these films have only become more and more violent since the PG-13 rating was first introduced in the ’80s — to the extent that PG-13 films actually have more gun violence these days than R-rated movies do.

This is because PG-13 is generally accepted as the four-quadrant rating, the one rating that's not too babyish or too gory. But because a lot of industry money relies on the fact that blockbuster movies get PG-13 ratings, it's essentially become meaningless. PG-13 isn't so much a single digit on a spectrum as a seal of assurance from a sex-obsessed organization that there's no sexy content in the movie. Because kids should see as much gunplay as possible—as long as there's no blood, or consequences to the gun battles, mind you—but heaven forbid a too-passionate makeout session fouls their pwecious eyes.