Can osmium stop a bullet

Answer 1

Theoretically speaking any material can stop a bullet, you just need enough of in the way. Practically speaking, there are two ways to stop a bullet: To bounce it, or to catch it. The two approaches have almost exactly opposite material requirements.

Bullet catching materials, like kevlar and lexan, operate by absorbing the kinetic energy of the moving bullet, slowing it to a stop before the bullet makes it through to the other side. To facilitate this, these materials generally have far lower density than the bullet materials, with either high ductility or flexibility (deform or bend easily). When two materials of differing densities impact, the denser material tranfers energy to the less dense material. This is basically why when you drop a beach ball and soccer ball of equivilent size, whith the beach ball on top, when they hit the ground the beach ball shoots up into the air. On the bullets impact, the kelvar/lexan will deform around the bullet, sapping its energy away.

Bouncing a bullet, which includes deflecting and smashing, generally requires a material with higher density and ridigity than the bullet material; something heavy and tough. High carbon steel has been a favorite for this application for over 300 years, even though steel is less dense. But, I digress, when a bullet impacts a denser material, its kinetic energy is bounced right back into the bullet. The bullet imediately accelerates in the opposite direction, facing a force of over 100 times the forcing of earth's gravity. The most materials, including lead and steel, aren't strong enough to survive this, and the bullet shatters, shooting fragments out in a roughly conical field. If a material is strong enough, or the bullet impacts at an oblique angle, the bullet can survive.

So, to answer your question: Yes osmium can stop bullet. As the densist naturally occuring metal, 30% denser than depleted uranium 238, the lead/steel/tungston bullet will bouce off, shattering into pieces. That said, it would be a very poor choice for this application. As a rare earth metal, osmium is surprisingly rare, and likewise extremely expensive. The current price is 61