Hunting season has arrived where I am located and I have had to choose a bullet/cartridge combination to hunt with. To do this I had to decide what range I would likely shoot, how much drop or drift I was willing to tolerate, the amount of recoil I could handle and lastly would the kinetic energy of the bullet be high enough to efficiently/ethically take down the game I was hunting. The last question deals with the amount of energy transfered to the target and essentially comes down to two things, how heavy is the bullet and at what velocity is it traveling when it hits the target. Hunters call this hitting power and the formula got me thinking, mainly about explosive's and how much of this is transferable to gasses. Now I know this is a touchy topic so right of the start I want to say I have no plans to build a bomb Im just wondering how something like this would be calculated. With a bullet it's fairly simple. Heavier and faster equals more energy delivered on target, density and aerodynamics allow you to deliver that energy at larger range's because a dense bullet with a sleek profile bleeds off it's velocity slower. But what about a gas? A bullet's density, volume and weight are all set so all that is needed to calculate hitting power is a known initial velocity. In a explosion the density of the expanding gasses their velocity and heat start off high and dwindle. So I wondered If you don't know mass how can the energy being delivered be calculated? I've been thinking about it for a little while and the best thing that I can come up with is molecules themselves, say an explosive detonates and produces a rapidly decompressing volume of co2, If you knew the detonation velocity could you not think of an individual co2 molecule in the same sense as a bullet? it has a set mass does it not? how does this work? what if you have 2 types of explosives one rapidly decomposes into say helium and the other into co2, If they both expanded outward at the same velocity the co2 explosion should impart more force then the helium explosion, right? could some one explain this? lastly I know that explosions move outward in all directions expanding in volume spherically unlike a bullet which only travels in one direction. So I have been trying to think of it in terms of a gas expanding down a rifle barrel (or engine cylinder), where the expanding gas wave has a fixed face (say 1 square inch). Can anybody explain this?, do Newton's laws apply to molecules? and are these two formulas in anyway related?