As a follow-up to my recent column on weapons, this one is on bullets.
Bullets were around thousands of years before firearms. Slings could use stones or purpose-made lumps of heavy metal, such as lead. Those last were bullets. The word comes from the French boulet, or small ball, which in turn comes from the Latin bulla, or knob.
No-one knows who actually first used a firearm to hurl a bullet. No-one knows who first purposefully made a tube for shooting a bullet. Once the properties of black powder were known, however, this use must have occurred quickly to many people independently. The fact that the dirty, smelly stuff could throw a stone or bullet much farther and faster than even the best slingsman would have made the extrapolation obvious to anyone with a bit of intelligence and imagination.
What held things back was materials science. Even modern black powder is far from an ideal propellant, and the crude bronzes, brasses and irons available during this period were far from the ideal gun-making materials. The mechanics of loading, aiming and firing were also very rough and impractical. Still, even the earliest, crudest "hand gonne" of the late Fourteenth Century was more effective than any sling and most bows, and lighter than ballistas and so forth. The effect they had on the battlefield wasn't limited to when they hit, either; the unexpected flash, the thunderous bang and the cloud of white smoke mystified and terrified those not used to them.
The earliest firearms bullets were monsters. In part this was because the smiths of the time could make large-bore guns more easily than smaller ones. As the metals and manufacturing techniques and even the powder itself were improved the bullets grew smaller. By the time of the US War Between the States most military long-arms were around sixty caliber. (That is, sixty hundredths of an inch in diameter.)
For the most part, progress was slow to this point. Oh, you'd occasionally have someone get a bright idea which actually worked and was accepted, but through much of the history of firearms a soldier might be issued a weapon his grandfather would have recognized. Or perhaps even the same weapon! The British Brown Bess musket - counting those converted to percussion cap ignition - was in service for over a century.
However, even during the Civil War there were radical new weapons in use. Repeating rifles and pistols firing complete cartridges, for example. These units of ammunition contained powder, bullet and primer in a single, handy package, resistant to weather and fast and easy to load into an appropriate gun. Things were changing, and the rate of change often left military planners far behind. Perhaps the most significant development in firearms during the Nineteenth Century was new propellants. "Smokeless" powders weren't entirely smokeless, but the quantity was greatly reduced over that produced by black powder. That was very useful in war, especially to those firing from concealment. More importantly, the properties of these new chemicals could be tailored to make far better propellants.
As a result of this improved chemistry - and improved metallurgy applied to firearms to enable them to contain higher pressures - velocities soared during the second half of the Nineteenth Century. With this new speed came a realization.
Bullet design had changed much by this time, going from simple, round balls of lead or soft alloys (ordinary military small arms ammunition is still termed ball) to the Minnie Ball. This was an elongated projectile with a conical or ogive nose and hollow base. On firing, the skirt of the base would expand to help engage the rifling and seal the gasses behind the bullet, increasing velocity.
There are other benefits for moving away from the simple, round ball bullet. The Minnie Ball has a higher sectional density than a simple sphere. That is, there is more material behind the frontal area. This gives better penetration on impact. Conical or ogival bullets also have less atmospheric drag, increasing effective range.
The two most important qualities in the "stopping power" of a bullet - that is, how quickly and effectively it stops an enemy from, well, doing anything - are shock (which depends on transfer of energy) and wound channel, the second of those depending upon both diameter and length for effectiveness. Both of these characteristics depend on the size of the bullet. If a bullet doesn't expand, or only expands slightly, it needs to start out large. If a bullet does expand significantly, its success depends on A) how much it expands while B) holding together to C) penetrate deeply enough to reach vital organs. To stop an opponent quickly you need a combination of quick deceleration, rapid expansion and deep penetration. The first two of those requirements go together; the third conflicts with them. To get all three requires a great deal of energy.
Lead and some of its alloys turn out to be very good at expanding under impact at low to moderate velocities without going to pieces. However, with the higher velocities possible in the new firearms, lead and the softer alloys turned out to not be very well behaved inside the barrel, and the bullets would fragment very quickly after impact. If you're using rifling - and by the time smokeless powders were developed just about everyone was for handguns and longarms firing single projectiles - lead will be stripped off the bullet by the lands in the bore. This is bad for that bullet, and very bad for the shooter when the next round is fired. Harder lead alloys will work to a point, but beyond that more is needed.
In metals strength is closely associated with hardness. The trick with bullets is to have something which will be dense enough to still pack a punch, malleable enough to "take" the rifling, strong enough to hold together in the bore, not so hard as to rapidly wear away the rifling, and malleable enough to expand in the target. For high velocities no one material could do all that. The answer was, of course, to use more than one.
Jacketed bullets began to appear, in a rapidly growing variety. Early jacket materials were cupro-nickel, nickel and copper. (Cupro-nickle is an alloy of copper, nickel and strengthening impurities, such as iron and manganese. It has the advantage of being very resistant to corrosion, even in salt water.) Even with that narrow assortment of materials the shape of the bullet, jacket and combination made for a huge variety. Full metal jackets completely enclose the projectile, but don't expand very well. Soft point jacketed bullets have a tip of lead or some other material sticking out past the end of the jacket. They expand, some quite well, but can be easily damaged in handling and loading. Hollow-points avoid the exposed lead tip but may not expand reliably without much fiddling in the design.
With the increased speed the new propellants and bullet jackets made possible, bullets began to shrink. Actually, given recoil they pretty much had to. While the diameter of bullets became smaller, shock effect was greater due to the higher velocity. Kinetic energy began taking over for brute force momentum, at least in rifles. Handguns, with their shorter barrels and greater recoil - both literal, due to lighter weight and perceived, due to being braced just with the hands - couldn't provide enough muzzle velocity with a good-sized bullet except in specialty designs.
As time passed and the science and technology improved, greater specialization began to be seen. The best design for a bullet depends on its job. Rifle or handgun? Military, police or civilian? High stopping power or high accuracy?
Military ammunition has requirements not found in other venues. For example, the enemy may be wearing body armor, and may be inside a vehicle (which may or not be armored) or behind a wall (which may be reinforced for defensive purposes). Therefore, penetration is of very high importance. Ball rounds are very good at penetration. Adding a steel or tungsten core greatly improves the penetration without altering the shape of the bullet. Instant stopping power is generally a secondary requirement, though much work has been done to improve that in bullets which meet the primary requirements. The fact that soldiers - both allies and enemies - are almost always in groups is also taken into consideration. Instant incapacitation with a single shot just isn't as important when several people are shooting at once. There are even international treaties making this official policy.
Police requirements are similar to those of the military but not quite as extreme. Police may be engaged in extended shootouts with felons inside buildings or vehicles. The sheet metal of a modern auto is pretty thin, and most modern handgun bullets can punch through this with plenty left to hurt or kill whoever is inside. Windshields are much tougher, and can even bounce a .357 Magnum bullet if it hits at a shallow angle. Side and back windows are less formidable, but can still drastically affect the path of a bullet. And, of course, there's far more to a car body than sheet metal. Mechanisms and reinforcements inside doors can stop bullets, for example. Still, except for the engine, automobiles aren't very good protection from bullets.
A military level of penetration is not good for most law enforcement use, since the bullet can go completely through the intended target and endanger bystanders. One reason the .38 Special LRN (Lead Round Nose) cartridge was used for so long (with the main one being sheer social inertia) was that it rarely overpenetrated while having fair stopping power. However, it was obviously underpowered for penetrating obstacles and as a low-velocity round produced little shock. Criminals receiving a fatal wound from a .38 Special bullet could still have time to kill others before finally expiring. Since police officers are usually alone or in small groups in the field, they needed something more likely to stop an opponent quickly. (Keep in mind that a law enforcement officer's sidearm is the emergency aid kit. Something which can always be carried in case of trouble, but not the preferred tool. If an officer knows there's going to be trouble, there's a longarm - shotgun or rifle - in the car.)
Police agencies for decades tried various combinations of cartridge and firearm (the .41 Magnum being strongly marketed as an ideal cartridge for those patrolling the highways) to try and find the ideal. The .40 S&W was developed from research done by the FBI with the 10mm cartridge. It is just slightly smaller in diameter than the venerable .45 ACP but is a modern, high-pressure round. Combining high velocity (for a handgun) with a decent diameter it is a very good stopping round. It can also fit ten rounds into a space which will only hold seven .45 ACP. Most police agencies today use the 9mm in any of several modern handguns, but the .40 is catching up.
Civilian handgun defensive rounds have yet a different set of requirements. Reliability in rapidly stopping an attacker is of paramount importance, since a civilian using a firearm defensively is usually alone, or the only one armed besides the assailant. Also, they will rarely be against someone wearing body armor or behind a significant barricade. Penetration must be sufficient to penetrate clothing, fat and muscle to reach vital organs. Anything more is wasted.
Some who read this may already be familiar with the Thompson-LaGarde Tests of 1901. Some may even know of the Thompson-LaGarde Cadaver Tests of 1904. The severe deficiencies of the .38 caliber service revolver had been made obvious in several then-recent military actions, and the Army wanted something better. As a result of these tests, real world experiences and other evaluations, the military services of the United States adopted the Browning M1911 in .45 ACP. This offered a cartridge with a velocity (and chamber pressure) typical for handguns of the day in a ball round (for legality and feeding reliability) with a large enough bullet diameter to have good shock and wound channel characteristics without needing to expand. It was roughly equivalent to the older .45 Colt military round in a (then) modern autopistol cartridge.
Now, these tests were deliberately focused on finding an effective military cartridge. Their relevance to civilian or even police applications is remote. Yet many to this day - and in spite of many developments in firearms and ammunition - still hold them to be revealed truth. At the opposite extreme are those who flatly state that the only thing they demonstrated was how stupid steers are. (The most common reaction of the test animals - steers about to be humanely slaughtered for food anyway - to being shot in the lungs was to look around to see where the noise had come from.)
Keeping in mind the specific goals of military handgun ammunition is important. The .45 ACP has a strong reputation for stopping a fight with one shot to anywhere on the torso, while it's greatest rival, the 9mm, is widely regarded as a wimp. Yet far more military forces - including most from the US these days - use the 9mm. There are many reasons for this. The 9mm is far from useless, and it has much better penetration than the .45. More rounds can be carried for the same weight and volume. Many consider the recoil to be more manageable, but this varies widely with the specific handgun. Finally, the handgun of whatever caliber is secondary to the rifle or submachine gun. Yet many parts of the US military retain the .45 ACP and more are going back to it, simply because the 9mm cartridge in military trim just isn't as effective as the .45.
For generations, cartridges and their bullets were designed through a combination of experience, intuition and testing. Some worked well, some worked poorly. Theories came and went as to what made a good self defense round. Today there are two primary schools of thought, which can be simplified into the theorists and the statisticians. The theorists have a model, tested in ballistics gel and/or other media, with results they believe to be significant. The statisticians compile actual data on shootings, usually those where a single shot to the torso ended the fight quickly and thoroughly.
Their results disagree. Not by a huge amount, but the difference is there, and it is significant. The statisticians tell the theorists that they need to change their theories. The theorists tell the statisticians that their data is at best anecdotal and badly analyzed, and at worst a work of fiction. Still, the two camps do agree in some areas. Personally, I lean strongly towards the statisticians. I'm an engineer, and am trained to select real world data over theory. As noted below, the difference is primarily in which specific bullet is best for a particular cartridge.
Today, with better materials and modeling techniques, as well as a large, organized body of data, bullets are tailored very exactingly. Expansion characteristics can be precisely set, based on diameter, muzzle velocity and bullet weight. No longer is the same basic design - usually proprietary by company - used for every hollowpoint. Instead, jacket thickness, cavity depth, core alloy and serrations can be adjusted to provide the desired penetration and expansion reliably for a specific goal. The difference in effectiveness comes from the breakpoints; where the designer of a particular load (the cartridge/bullet weight/velocity combination) believes the balance between penetration and expansion should be.
If you believe the statistical data, these days the difference between the best-performing rounds in various calibers is a matter of only a few percentage points. Yes, specific cartridge/bullet combinations are better in specific situations. For general self defense use there's at least one cartridge in all of the major calibers which will reliably stop a fight with a single shot to the torso well over 90% of the time.
What is a major caliber? These include (and while I'll try to be thorough I may miss some) 9mm, .45 ACP, .357 SIG, .40 S&W, 10mm, .45 Colt, and any of the centerfire Magnum cartridges except perhaps the .32 H&R and .327 Federal. Note that many of these are so potent that most beginners should not consider them. Many are also not chambered in any autopistols suitable for self defense. (Note that this definition of major caliber is for stopping an enemy. There are shooting competitions where some of these cartridges would not be considered major caliber.)
Lesser cartridges are far from harmless. For example, pistols chambered for the .380 ACP are very popular as a hideout or backup gun among law enforcement officers. The best of the loads for this are fairly effective, being somewhere in the 70% range for one-shot stops. (This is still better than the .38 Special with a traditional load, which is in the mid sixties.) However, the round seriously lacks penetration. One member of an online shooting list I belong to described an accidental discharge of a .380 auto pistol in his kitchen, caused by a defective striker in the pistol he was chambering the round in. The bullet bounced off a single pane glass window. (He didn't mention bullet weight or design or angle of impact.)
However, the size and weight ranges of .380 pistols overlaps largely with those of defense-suitable 9X19/9mm Parabellum pistols, so there's really no reason to go with the less powerful round for normal self-defense, except for people who have such low hand strength that they can't cycle the slide on any 9mm. There are some models of .380 ACP pistols which are loaded by tipping the barrel up and sliding a cartridge into the chamber, rather than racking a spring-loaded slide.
So there you have a brief (yes, really) overview of how bullets work, their history and the current state of the art. This is a complicated subject; people can and have spent decades on it. This is partly because the process of making a better bullet is ongoing, and there's always something new coming along.
This document is Copyright 2010 Rodford Edmiston Smith. Anyone wishing to repost it must have permission from the author, who can be reached at: firstname.lastname@example.org