Why lead is used to build bullet and not other, harder metals?
In: Other
[removed]
There absolutley are plenty of other types of bullets for all kind of reason and purpose. Lead is just heavy, it has the most mass per volume meaning the bullet is heavy and has more power for that reason.
It depends on the use of the bullet. Armor-penetrating rounds use metals like tungsten to help penetrate. They want the round to keep its shape on impact to focus the energy on a small area. But tungsten is expensive and hard to work with. You could use aluminum, but that is very light. So air resistance will have a significantly higher effect, reducing range and accuracy. The lighter weight also means it will impact the target with less energy (assuming same velocity as a lead round). Lead is commonly used because its cheap, dense, and malleable. When shooting an unarmored target, like when hunting, you want the round to deform when it hits to better transfer energy and cause damage. You are trying to kill the animal as quickly as possible so it a) doesn’t suffer and b) doesn’t run making you have to track it down and then carry the carcass that much farther. You also have to consider barrel wear. A hard metal will scrape and wear down the barrel faster, making it less accurate and lose power. Even armor-penetrating round usually have a softer metal like copper as a jacket to reduce barrel wear.
Lead is heavy which means once it starts moving it has momentum, so a lead bullet has a lot of energy once it hits the target, on hitting the target it can transfer a lot of that energy into the target and damage the target, the actual toughness of the material matters less than the momentum, tanks use depleted uranium rounds for the same reason.
Assuming the propellant (the gunpowder) is powerful enough to get a heavy bullet moving as fast as a light bullet (and it typically is), a heavier bullet will have more kinetic energy (and momentum, that has advantages separate from high KE) than a lighter one.
Lead is very heavy and cheap. Other metals are either too light, too expensive or just don’t offer enough of an advantage to bother with, at least for non-military applications. (Although you’ll sometimes see things like brass slugs for shotguns or “elephant” rifles, they’re harder than lead and not as likely to disintegrate on impact, so they might be legitimately useful. There’s also lots gimmick ammo out there, but most of it is no better than lead jacketed in copper, and virtually none of it is worth the price.)
Also, back in the day when manufacturing technology was less advanced, it was a *lot* easier to make consistently-sized spheres from lead than from other metals. You don’t need a very hot fire to melt lead, and it’s so soft that any imperfections or flash left from casting it in a mold you can just clip off with a simple tool, or even trim off with a knife.
Because the aim of q bullet is not maximum possible penetration, it is maximum transfer of energy. Very hard tungsten or steel penetrators are sometimes used to defeat armor but generally speaking, they cause smaller and less damaging wounds that are less likely to disable an enemy.
Lead is soft and dense which are both useful traits for bullets as they engage with rifling better, and high density means they have more energy at a given size and speed, and they deform when striking a soft target which allows them to transfer their energy and create larger and more debilitating wounds.
To maximize performance of the bullet, it has to seal VERY tightly to the inner bore of the barrel (and chamber rpessures are very high, tens of thousands of PSI or more). To do this we rely on a process called “obturation”, basically the bulled gets squeezed down a bit as it enters the barrell, and the otuer surface of the bullet deforms until it conform perfectly to the bore, sealing off all the high rpessure gas behind it.
For this to work effectively, the metal has to be soft enough to deform easily. Lead is very soft. Lead also has the benefit of being very dense (so you can heavier bullets, which has ballistic benefits), and also having a very low melting point (so that you can melt lead into a simple mold and make your own bullets over a campfire or whatever). So it was a great option in the early days of guns (and still is for many uses).
However as more modern guns reached higher and higher bullet velocities, and mdoern gunpowder burned with higher pressures, we found that lead started to have some problems. It was almost TOO soft and had TOO low a melting point, and in high eprformance rifles you might have problems shooting sold-lead bullets. So we developed metal “jackets”. This is a thin layer of some other metal (usually a copper allow, soemtimes steel, etc) that is tougher and harder than lead, but still thin/soft enough to do the sealing/obturation part. These will often still have a lead “core” inside them, because lead is still very dense, and its cheap, and being so sfot can make the bullet expnd more on impact, doing more damage. but there are also modern “monolithic” copper rounds that are just a single piece of pure solid copper. There are also some specialty rounds that would include otehr metal cores. This might be a tungsten ‘penetrator’ to help the bullet go through armor, or sometimes just a piece of mild steel (fairly soft) that was included to give the bullet the correct weight or center of gravity or other reasons.
For guns chambered in older calibers, or guns that inherently shoot at lower velocities and pressures (many pistols/revolvers, etc) you can still use plain old solid cast-lead bullets, and they are a very economical choice if so. But in most cases a copper jacketed bullet is going to be a better choice overall.
Density and cost. Nothing else comes close. Special bullets can be made from other materials. Anti-armor projectiles are sometimes made of tungsten, which is very expensive, or depleted uranium. Depleted uranium is pretty cheap if you are a country enriching uranium for fuel or weaponry. A complication – high velocity bullets made of just lead will leave lead fouling in the barrel of a gun. High velocity bullets will have a lead core jacketed with copper or some other gilding metal. Small arms bullets made for the military must be fully encased as required by the Geneva Conventions. (Full metal jacket). Target ammunition is also full metal jacket because it is cheaper to manufacture than soft nosed bullets.
The ideal bullet is made of a dense material, as denser bullets can absorb and carry more kinetic energy for their size, which means they slow down less due to drag as they travel through air or things. Lead is ideal for this reason, as it’s denser than pretty much any commonly available material at 11.3 g/cm^3 (copper is 8.9, steel is ~7.8)
If you fire a lead or steel bullet of the same size and shape out of a gun, the steel bullet comes out faster at first because it’s lighter than the lead bullet, but slows down more rapidly because it’s carrying less energy. The lead bullet will carry more energy and better maintain it’s speed, giving it more range and power.
Lead also has the benefit of having a low melting point and being very soft, so it can be easily cast or formed into bullets. Its softness also means it can be engraved by the rifling grooves without damaging the gun barrel. It’s softness also causes the bullet to balloon or mushroom out when hitting something, which increases lethality on human or animal targets. So it’s ideal for making bullets. Maybe the only thing better for these factors will be gold, but that will make for a very expensive bullet.
That being said, lead does have its drawbacks. In high velocity or powerful loads, lead bullets can melt or stripped away as it is pushed through the barrel due to the intense heat and stresses from friction. Jacketed or patched bullets were develop to get around these issues, by using another material like copper or paper to wrap around the outside of the lead. Copper or bronze jackets are ideal for this because they’re stronger, has low friction, and high melting temperature – while still soft enough to engage the rifling grooves without damaging a steel gun barrel.
A wide range of other materials have been used for making bullets, with or without combining with lead. The French military rifle cartridge used in WWI (8mm Lebel) had a solid bronze bullet. Softened mild steel being several times cheaper than lead is often used for bullets when the military wants to save money, as in the case of a lot of Soviet or Chinese military 7.62mm ammunition meant for the AK. The Spanish experimented with a strange one having a aluminum core and copper outside. Armour piercing bullets have a tungsten carbide or depleted uranium core, which are very hard and denser than lead, making them more powerful ballistically and ideal for punching holes through armour.
Latest Answers