Penetration of Automobile Glass.

You might be faced with the need to fire through

car door glass at a perp tying to take over your car.

Car door glass is much different from windshield glass.
The door has a single pane tempered and designed to
break into small pieces on heavy impact.

But to penetrate the laminated polymer-reinforced
double-pane windshield, you need at least 230ft-lb with

hard-point ammo, and more energy with soft points.

This means a 9x19mm must have a copper jacket point

fired from a barrel at least 3.5" long, and nearly
perpendicular to the windshield.

FBI automatics are now 357sig or similar power to deal

with windshields and doors (the bullet is their business).

Concealed-carry ammo is not for windshields, unless you

are willing to pack a 357, 40, or similar.  But lighter ammo

can be effective through car DOOR glass, since that glass

is designed to break into small pieces when struck hard.

The first shot will at least break the glass, with the second

shot having full effect on the perp.

If you fire a pocket gun from inside toward the front, reach

around the windshield.  I won't mention teflon or steel, but

those are available somewhere.  I was surprised that the info I

found is that teflon might increase velocity, and help penetration
of glass and metal, but not into ballistic vest materials.