Power: Living in the Moment of Inertia
When most people talk about the power of a cartridge they are trying to quantify its effectiveness on game. This is a daunting task, and as of yet there is no universally accepted method of determining the relative power of different cartridges. The most commonly used trait is kinetic energy, which is very useful for comparing bullets of relatively equal caliber, but is almost useless when comparing bullets of dissimilar calibers. To understand why kinetic energy is not a universal measure for the relative power of different cartridges you have to understand a little about the two qualities which it represents: Velocity, and mass.
Velocity has two main effects on a bullet: Trajectory, and the behavior of the bullet upon impact. Generally speaking, the faster a bullet is traveling when it strikes a target the more likely it is to dissipate its energy through expansion or fragmentation rather than penetration. In an extreme example, there have been instances in which a bullet has been fired at such a high speed that it fragmented upon exiting the barrel and encountering air. To prevent this, bullet manufacturers alter the design of a bullet so as to match it to the speed at which it will be fired. Rapid expansion is actually a desirable trait in cartridges which are meant for taking varmints though for larger game, where penetration is more important, a more controlled rate of expansion is desired. In other words, the faster your bullet is traveling or the bigger your quarry, the tougher the bullet has to be.
The effect that the mass of a projectile has on the power of a cartridge is not a simple thing to quantify due to the fact that it doesn't take into account the shape of the bullet, which could either be narrow and long, or wide and short. Generally, the heavier a bullet is within a certain caliber, the farther that bullet will penetrate into a given medium. The quality of being "heavy for caliber" is usually expressed as sectional density, with higher numbers representing proportionally heavier bullets. The reason a higher sectional density bullet demonstrates deeper penetration than one with a low sectional density is a result of its mass being focused into a smaller area upon impact. Because of this, it is possible for a bullet with less mass to penetrate farther than one with more mass despite having less kinetic energy, so long as the lighter bullet has a higher sectional density than the heavier one. This is why Kinetic Energy is a good indicator of relative power if the bullets are close to the same caliber, but not if they are of dissimilar calibers.
From all this we can say that if you want a powerful rifle you should look for something that fires a large caliber bullet with a high sectional density at a very high velocity. However, any cartridges that meet this description will have one major drawback: Recoil. The .223, a variation of which is widely used by military forces throughout the world, can be shot comfortably even by children, and produces about 3ft-lbs of recoil. Alternatively, the .30-06 produces about 20ft-lbs of recoil and is about the hardest recoiling cartridge which is comfortable for most people to shoot. Compared to cartridges like the .375 Holland and Holland Magnum which produces about 36ft-lbs of recoil, or the .460 Weatherby Magnum which produces just shy of 100ft-lbs, it becomes obvious that caliber choice must be a compromise between the power needed for a specific task and recoil.
Stay tuned for part 5 "Rifle Actions: Asking a Loaded Question".
Velocity has two main effects on a bullet: Trajectory, and the behavior of the bullet upon impact. Generally speaking, the faster a bullet is traveling when it strikes a target the more likely it is to dissipate its energy through expansion or fragmentation rather than penetration. In an extreme example, there have been instances in which a bullet has been fired at such a high speed that it fragmented upon exiting the barrel and encountering air. To prevent this, bullet manufacturers alter the design of a bullet so as to match it to the speed at which it will be fired. Rapid expansion is actually a desirable trait in cartridges which are meant for taking varmints though for larger game, where penetration is more important, a more controlled rate of expansion is desired. In other words, the faster your bullet is traveling or the bigger your quarry, the tougher the bullet has to be.
The effect that the mass of a projectile has on the power of a cartridge is not a simple thing to quantify due to the fact that it doesn't take into account the shape of the bullet, which could either be narrow and long, or wide and short. Generally, the heavier a bullet is within a certain caliber, the farther that bullet will penetrate into a given medium. The quality of being "heavy for caliber" is usually expressed as sectional density, with higher numbers representing proportionally heavier bullets. The reason a higher sectional density bullet demonstrates deeper penetration than one with a low sectional density is a result of its mass being focused into a smaller area upon impact. Because of this, it is possible for a bullet with less mass to penetrate farther than one with more mass despite having less kinetic energy, so long as the lighter bullet has a higher sectional density than the heavier one. This is why Kinetic Energy is a good indicator of relative power if the bullets are close to the same caliber, but not if they are of dissimilar calibers.
From all this we can say that if you want a powerful rifle you should look for something that fires a large caliber bullet with a high sectional density at a very high velocity. However, any cartridges that meet this description will have one major drawback: Recoil. The .223, a variation of which is widely used by military forces throughout the world, can be shot comfortably even by children, and produces about 3ft-lbs of recoil. Alternatively, the .30-06 produces about 20ft-lbs of recoil and is about the hardest recoiling cartridge which is comfortable for most people to shoot. Compared to cartridges like the .375 Holland and Holland Magnum which produces about 36ft-lbs of recoil, or the .460 Weatherby Magnum which produces just shy of 100ft-lbs, it becomes obvious that caliber choice must be a compromise between the power needed for a specific task and recoil.
Stay tuned for part 5 "Rifle Actions: Asking a Loaded Question".