Bullet Resistant

There is no such thing as "Bullet Proof." the criminal will just use a heavier, larger caliber and faster bullet.

There are 3 variables to consider in determining and understanding Bullet Resistance:

Weight. The heavier the bullet the more impact it will generate.
Caliber. The larger (higher) the caliber the easier it is to stop the bullet at low velocity.
Velocity. The faster the bullet travels the more difficult it becomes to stop.

.38 caliber and .45 automatic are large caliber bullets traveling at low velocity which makes them relatively easy to stop.
.357 and .44 Magnums are large caliber, heavy bullets, traveling at highvelocities. This relates to high knock down impact with high penetration.

Powder charge and barrel length affect “velocity.”

To increase powder charge, is accomplished by increasing the brass casing to hold more powder.
To contain the explosion and direct the energy longer generates more speed. The longer the barrel the faster the bullet with everything else being equal.

There are even more things to consider. There are several types of bullets designed for different purposes. “Standard” types most common are:

Lead= high impact, low penetration, accuracy, best use is target shooting and close combat.
Semi Jacket is a partially encased lead copper jacket= accuracy, longer range, medium impact, high penetration = penetration before expansion on impact.
Hollow Point Semi Jacket = long range, high speed, light, maximum impact, light penetration, maximum damage
on impact.
Full Copper Jacket = long range accuracy, automatic weapon efficiency, minimal impact, high penetration.

Less common types of bullets sometimes specified with government or international applications:

Explosive Heads = detonate on impact, designed for maximum tissue damage.
Steel Jacket = completely encased lead jacket for maximum penetration.
Armor Piercing = solid steel bullet for penetration of metal surfaces.
Teflon Coated = steel or copper jacket bullet lubricated with teflon for penetrating hard surfaces.

Bullet Proof cannot be achieved because there are so many variables to take into account when considering bullet resistance.