The same way swords do: they hit armor, strike a nearby piece of cover and spray you with shrapnel, or cause a flesh wound. The one that drops you to 0 may be a mortal wound (you die) or not as bad as it first looked (you don't die). The whole combat system is abstract, including what "hit" means.You may be watching too many movies. How does a gun do damage that doesn't reduce combat effectiveness immediately?
In game he is a fifth level fighter so he fights on. In the movies the bullet would shatter on his armor and a splinter would lightly open a cut on his cheek. He would rattle of a one liner and in the next 40 rds blow up half of Neverwinter. Only to cry with the cute cleric babe poured moonshine ( potion of cure light wounds) on his cut.Actually, hold on. In your description, does ranger Rick keep fighting, or is he down too?
DnD combat can't model accurate archery for the same reason, then. I'm not even that good an archer, and I can fire off shots and much more quickly than 1-2 per 6 seconds. It takes me about 1.5 seconds per arrow, if I'm doing a full draw, and holding my arrows in my bow hand. Still just under 2 seconds if I'm using a hip quiver instead.Too many movies. A modern gun fires how many rounds per second? D&d combat system can't simulate combat with modern weapons mostly due to the time scale relative to human reaction times. In medieval combat, there was lots of circling and feinting.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.