That depends on a lot of factors including your definition of armor piercing.
Body armor (your "bullet proof vest") comes in different levels or ratings of protection. NIJ Level IV is rated against some military designated AP bullets.
A 30 caliber AP cuts like butter through 1/2" plate steel. Half way through 3/4" plate steel. A Humvee is 3/8"
Armour piercing-yes.
No one armor piercing bullet, so there is no one cost. Most are inexpensive to make- less than $1 per bullet.
Nothing is really bullet proof. Anything labeled as such can always be beaten by a faster and/or heavier bullet. Things can be armored, bullet resistant, impact resistant ASO. And the best stuff for getting through things like that are armor piercing rounds.
No way to answer. What type of steel? What range? What weapon is being fired? What barrel length? Armour piercing at 400 meters
There are several different technologies with armor-piercing bullets. A common one is for the bullet to have a thin core of steel, or other hard metal. Typically bullets have soft lead surrounded by soft copper. When these bullets hit something, they deform, usually increasing their diameter as they penetrate. Most armor exploits this property. Steel will not deform like lead & copper, and is much more likely to penetrate deeper than a regular bullet.
Yes, and no. There are certain bullets that are designed with extreme piercing in mind. Such bullets are important to the military. Most bullets, however, are not strong enough to pierce steel. It also depends on the type of steel involved. A 20 foot thick piece of steel could assuredly not be pierced by ANY bullet that is produced today. But a baking sheet thickness of steel could be pierced by steel. About 2 inches of steel can stop a bullet for most bullets :) If you're considering using a piece of steel to wear to get shot in- Just say no to stupid ;)
Depends on the thickness of the platinum, the speed and weight of the bullet, and what the bullet is made of. A.50 caliber armor piercing bullet will shoot through some thicknesses of steel or concrete.
No one answer to your question. This would depend on the particular alloy of titanium, how it is treated, and the bullet that it is trying to stop. Some very large caliber armor piercing bullets are VERY hard to stop.
It all depends on the type of bullet and type of armour. A 5.56 armour piecing round will penetrate light armour - like that found on Russian APC's but will just "ping" off of a tank. A normal soft point or hollow point will just deform on all armour.
There are many materials with bullet proof properties including Kevlar, Lexan, Titanium, Steel and Carbon Composites. Keep in mind that "bullet-proof" is a relative term. Armor-piercing bullets are designed to be able to penetrate most of these so-called "bullet-proof" materials that will do a decent job of stopping normal (non-armor-piercing) rounds.
It's quite likely, considering most 7.62mm cartridges are made to penetrate light armour (body armour and sheet metal).
The size of a given bullet is determined by its diameter, and its weight. The size must match the size of the barrel it will be fired from, and heavier bullets will be longer. With cast lead bullets, after casting they are pushed through a machine called a die. This squeezes the bullet down to a precise diameter- this is called SIZING.