Perhaps in interesting topic.
I have a .308 win, love it for hunting, but I have recently began to think hard about getting something with some more umpf
So here is the topic. What has better overall stopping power, or what makes a bigger difference. Bullet diameter or velocity considering bullet weight would be roughly the same based on availability.
338 Federal with 225gr travelling at 2450 approx fps.
300 win mag with either 220 or 230gr travelling at approx 2650 approx FPS.
My velocities may not be perfect but the point remains, a 308 cal projectile travelling faster, than a wider diameter but slower 338
Thoughts?
Edited, Bullet diameter vs Bullet speed for a faster drop of an animal (moose bear)
You have missed a very important element of terminal performance, which is bullet construction. Mass X velocity squared gives us an idea of what can be expected from a given caliber, weight, and velocity, but without knowing the construction of the bullet, we don't know if its suitable for elephants, deer, crows, or just punching paper. When selecting a bullet for hunting, the density of the animal must be considered, and we should have some expectation of the amount of penetration needed to ensure a clean kill.
Perhaps the first thing to consider is how a bullet kills game. The animal dies when oxygen no longer reaches the brain, causing the brain to die. This can be achieved by interrupting the flow of oxygenated blood to the brain, by destroying the lungs, the heart, or through simple blood loss. It can also be achieved by the destruction of the central nervous system which controls the anatomical functions of the body. Finally, the bullet can kill by creating a wound which is not immediately fatal, but becomes infected, resulting in a long unpleasant death for the game.
Most game in North America can be killed with a bullet/velocity combination that produces 12-18" of penetration, but there are exceptions such as bison or big bears at close range, where 30" of penetration is comforting, and there might be an argument that 24" is beneficial on elk and moose. Penetration of an expanding bullet is reduced with the increase in impact velocity, since the bullet changes shape more quickly, which also produces a wider-shallower wound channel. Penetration of a well designed non expanding game bullet increases with the increase in impact velocity, since there is no change in shape, and the shape enhances straight line penetration. If an animal is big enough, and if shot with two bullets, one which expands and one which does not, the wound volume will be identical if bullet weights and velocities are the same; only the shape of the wound will be different.
There is no ideal cartridge or bullet for all game under all circumstances, although some do a number of things very well. If we say for example that a .300 Winchester firing a premium bullet is necessary to kill a moose, the assertion will be met with laughter and the fact that a million moose have been killed with cup and core bullets fired from .30/30s, will be quickly pointed out. The point is that the .300 will kill a moose in circumstances where a .30/30 will not, and a bullet which expands and penetrates sufficiently to use on a moose at .30/30 velocities, is completely unsuitable when the impact velocity is 800 feet per second faster.