I'm writing a book and in it there is a character who can accelerate objects to extreme speeds in one direction. His weapon of choice is a custom built gun that is similar to a BB gun. It fires 5mm tungsten rounds that weigh 1 gram (for simplicity). Normally the gun is just a non-lethal air powered gun, but when he uses it he can accelerate the load to 0.01% the speed of light. The problem is I don't know how much damage this would do. I want him to be able to blow people way to the point that they are just a stain on the side walk, to wreak tanks in a single shot, blow holes through steel walls, not to level a city. I am worried that 0.01% the speed of light might be over kill so my question is how much force would this (shooting a 1 gram 5 millimeter ball at 0.01% c) produce and what type of damage would it do. For example if this was shot at a 5 meter x 5 meter iron wall that is a centimeter thick. Also this would blow someone up right? I'm not well versed in high velocity impacts. tl;dr: 1 gram 5 millimeter ball projectile moving at 0.01% the speed of light hits a 25 meter^2 iron wall that is 1 centimeter thick and the projectile hits the wall perpendicularly. How much damage does this do to the wall an the surroundings? How long could the ball travel without being evaporated or otherwise destroyed? If you were firing this how far away would you want to be from the impact site? In;b4: Ignore newtons third, there is no recoil (magic) Fallow up question: How would this be effected if the character also had a power that could increase the strength of molecular bonds, causing the ball to be extremely durable to the point that it would survive the impact? or just durable enough to survive the travel?