Each year more than a hundred thousand Americans
are shot by firearms.
And although guns get a lot of attention,
wounds are caused by bullets.
And bullet wounds are getting more devastating,
in part because of design and physics.
The damage depends on the speed of the bullet
and its ability to transfer that energy to its target.
All of that boils down to mass, speed and shape.
Take two of the most popular 9 mm bullets.
They're commonly used in handguns.
The top one here has a full metal jacket.
The rounded tip protects the front of the bullet
and helps it keep its shape.
It enters, travels straight through and then
exits, taking some of its energy with it.
But bullets don't always fly straight.
At less than a hundred yards they can pitch
or wobble.
If it hits a target at this distance, the bullet could tumble
opening up a wider wound.
The bullet could even fragment.
This is a 9 mm hollow point.
It's what most police use.
The tip is designed to open up.
This larger surface area creates extra friction
that slows down the bullet as it passes through tissue
and eventually stops.
All of the bullets energy gets absorbed.
A shock wave opens up a temporary cavity
and the tissue in that space gets damaged
and bruised.
Hollow point bullets are less likely to
come out the other side of a person and
injure a bystander.
That's one reason police use them.
But when it comes to destructiveness,
what's more important than shape is speed.
The .22 here is a common bullet.
People use it for target shooting and hunting.
It's moving so slowly that it tumbles and
then comes to a stop.
But the .223 is moving more than three times faster.
This bullet is used in AR-15-style guns.
They're some of the most popular recreational weapons in America.
More speed means more energy and all
that energy has to disperse somewhere.
The shock wave can break bones and
rupture organs.
So speed, mass and shape --
that's what determines how destructive bullets are.
And more Americans than ever are getting
shot with larger, faster, better-designed bullets.
This is Let's Talk, NPR's news explainer show.
Make sure to subscribe to our YouTube channel
and check out our other shows.
I'm Rebecca Hersher and this is NPR.
