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Sunday, July 3, 2016

Every thing about Bullets

Ammunition can be a very intimidating subject for those who do not know much about firearms. Selecting ammunition for hunting or personal defense is a very important decision with strong implications for the performance and safety of your firearm. With lots of opinions, misinformation, and geek-speak floating around on the topic, it can be overwhelming to the point of exasperation.
The good news is, it’s actually a really simple topic, once you understand some of the basic terms. So, with that in mind, let’s learn about various types of ammunition, some of the common lexicon, and how to judge what is “best” for you.
Ammunition is generally expressed in a measurement. Most of the world uses a metric rating, while the commercial market in the United States uses a U.S. standard measurement. This can create some confusion, but more on that later.
The measurements in metric are almost always a “diameter to length” ratio; for example, a bullet in the caliber:
  • 5.56x45mm is 5.56mm wide and 45mm long
  • 9x19mm cartridge is 9mm wide and 19mm long
  • Shotshells are measured in “gauge”, with a lower number being a larger diameter.  Typical 12 gauge shells are 70mm long, which works out to be 2½”, but offered in a 3” magnum as well
Before we go on to a quick look tying measurements to the actual cartridges, it’s important to note that a cartridge is made of four components:
  1. Case (generally brass, nickel, or steel)
  2. Primer – an ignition for the propellant; look for the round dimple on the base of the cartridge.
  3. Powder/propellant – also known as “gunpowder”
  4. Projectile – also known as the bullet (technically it's the only part of the cartridge that is a bullet)

Types of Bullets

There are several other types:
SP – Soft Point – the tip of the bullet is left uncoated (exposed lead)
AP – Armor Piercing – this ammunition has a alloy core, instead of lead
BT – Boat Tail – this means that the rear end of the cartridge is tapered to stabilize the projectile in flight
BTHP – Boat Tail Hollow Point is a combination of the Boat Tail and Hollow Point Features
This image demonstrates the cartridges and lists them below in order of descending length:
  1. 12 gauge Shotshell
  2. 8mm (7.9mm) Mauser
  3. 7.62x54mm Russian (Notice that this cartridge does not have a “rim” at the base)
  4. 7.62x51mm or .308 Winchester
  5. 7.62x39mm Soviet
  6. 5.45x39mm Soviet
  7. 5.56x45mm NATO or .223 Remington
  8. .44 Magnum (Notice that this cartridge does not have a “rim” at the base)
  9. .45 Automatic Colt Pistol (ACP)
  10. 9x19 Para. (Also known as: Luger, Parabellum, and commonly known as simply “9mm,” although there are other 9mm’s which have different lengths.)
  11. .22 Long Rifle
Again, a look at the calibers from the top, to compare their relative diameter:

Elements of Performance:

Now that we’ve had a quick look at the physical characteristics of these cartridges, let’s talk quickly about some elements of performance. This topic is the subject of many books, articles, and Internet posts and would take up a tremendous amount of space to fully explain in one article, but with an understanding of what these things mean, you can go forth and make decisions based on the knowledge you develop.
The word “Ballistics” itself is from the Greek Word ‘Ballein’, which means “to throw’. Just like a football or baseball, when a bullet is fired, it follows a trajectory and is assigned a velocity, and these two things account for the lion’s share of how a bullet performs. The bullet doesn’t fly in a straight line, but is ‘lifted’ and then begins to ‘drop’ as it loses velocity.
That can be illustrated by the following examples of ‘trajectory’:
POA = Point of Aim
POI = Point of Impact
Figures on the left are height in inches
Figures on bottom is distance in yards

Bullets come in various types that are denoted as suffixed acronyms; these bullet types can be visualized hereThe vast majority of bullets are constructed of a solid lead core and a copper covering (called a “jacket”) that contains the lead. Lead is used because it’s an extremely dense yet cheap metal, making it perfect for giving projectiles their weight while keeping the overall size small. Copper is used because it is strong enough to keep the softer lead in shape, but is soft enough to allow the rifling to grip the bullet.
As can be seen, these are not ‘straight lines’, and bullets follow an ‘arc’. This is often considered in how ‘easy’ or ‘difficult’ a particular caliber is to shoot – flatter shooting rounds (like the 5.56mm or 5.45mm) are very easy to hit with because they undergo very little change in elevation over the course of flight.
The bullet, upon impact, is assigned an “energy” rating, which is usually expressed in pounds per square inch, and this value is calculated using the bullet's velocity and mass. I personally prefer to use Joules, as it lets me keep my conversions to a minimum, but we can use the standard formulae to derive a figure:
Kinetic Energy is equal to mass (grams) times velocity squared (meters per second), which would look something like this:
E_k = \begin{matrix} \frac{1}{2} \end{matrix} mv^2
It’s important at this point to discuss a very flaccid term: “stopping power”
This theoretical amount of energy is what people attempt to use to refer to the amount of energy transfer required to make a human being “halt”. The reason that this is such a dangerous misnomer is that in order for a person to be literally ‘stopped’ by the force of a bullet, the person firing that bullet would have to feel an equal or greater amount of recoil.
This means that when a person or animal is struck with a bullet, the impact is less than or equal to the recoil felt by the person firing the bullet, as per Newton’s laws of motion.
So, from this, we can assume henceforth that a person or animal reacts to the psychological pressures of the physical injury and the ‘surprise’, rather than the actual force of the impact.
In short, there is no numerical threshold that can be relied upon to produce ‘stopping power’.

Thoughts on Ammunition:

Ammunition (and caliber) is a hotly contested issue. The 5.56mm has been lauded as inefficient and underpowered, while the Afghans nicknamed the Soviet 5.45 x 39mm “The Poison Bullet” due to the smallest injuries resulting in death.
There’s less than 0.11mm difference between them, so why the disparity? Truthfully, it doesn’t exist.
Design has a lot to do with it – the Russians designed the 5.45 with a hollow cavity in the rear of the bullet, which causes its lighter rear end to ‘turn’ immediately upon impact, sending it on a wildly erratic path once it enters tissue, a process called “keyholing”. The 5.56mm used by American forces, by comparison, is a simple, jacketed ball round, not meant to maim or cause excessive wounding. Bullet design has a lot to do with what the bullet is good at, as well as what it is not.
Ball ammunition, for example, is notorious (in both handguns and rifles) for passing through the intended target (or drywall, OSB, vehicles, and so forth) and striking ‘unintended’ targets. For this reason, Hollow Point ammunition is used by most professionals and citizens. This is because upon striking a target, hollow points rapidly expand in diameter, which creates drag and slows the projectile, making it both larger and more likely to strike vital targets, while decreasing the likelihood that it will pass through the target.
Another important note to make is that Hollow Points, though they sound terrible and nefarious, are actually far safer to use for defense than is ball (which sounds pretty unimpressive) because of this reason. Hollow Points are *not* “Armor Piercing” rounds, and this means they are not regulated in any capacity (yet) though some are restricted to Military and L.E. purchases.
Armor Piercing rounds, while we’re on the subject, have a misnomer.
The body armor worn by police officers (Commonly referred to as IIIA, soft armor, or Kevlar) is penetrable by nearly every single production rifle round that’s above .22 caliber. For this reason, all rifle rounds could be considered “armor piercing”, unless we are discussing military-grade armor (Commonly known as IVA, SAPI or Ceramic Plate armor), which is made specifically to stop military ammunition. Therefore, the only “armor piercing” ammunition that’s made is made for rifles, and it only applies to military grade SAPI plates.
This is an important academic point as the political rhetoric continues to boil over – as a ban on “armor piercing” ammunition could easily be taken to mean “all rifle calibers other than .22”.
So, when you select ammunition for hunting or personal defense, it’s important to learn:
  1. The ballistics of the cartridge you’ve selected (how ‘high’ or ‘low’ will the bullet be at a given distance?)
  2. How prone will it be to passing through walls, tissue, or vehicles? (Very important for safety and liability reasons – it’s incumbent on you to know where every round you fire goes!)
  3. Is the type of ammunition you’ve selected appropriately to the task at hand. For example, there’s no reason to buy hollowpoints to practice your marksmanship! They’re more expensive, and will perform better, but the ball will serve just fine for this role.
Also, if you’re very new to owning firearms, double-check to be sure that you’ve got the right cartridge… By now, you’ll have noticed that there are very common cartridge diameters. The “7.62” for example, could refer to 7.62x25 Tokarov, 7.62x39 Soviet, 7.62x51 Winchester, 7.62x54 Russian, or 7.62x59 (commonly known as .30-’06)!  As well, “9mm” could mean 9mm Kurz (.380ACP), 9x18 Makarov, 9x19 Para., or 9x21 Largo.

The copper jacket starts out as a cup, having been cut from a long sheet. Through a process called “drawing,” the cup is lengthened and shaped to fit the profile of the projectile they’re making. These cups will eventually end up as jackets for 5.56 NATO rounds.
However, while this process is very efficient, it’s extremely difficult to actually get the metal to encase the entire lead core without any gaps. To keep production costs down, bullet manufacturers usually leave one end of the projectile open. Which end is open – and how that’s done – determines the classification of the projectile.

Full Metal Jacket (FMJ)

FMJ bullets, c Nick Leghorn
“Full Metal Jacket” or “FMJ” projectiles usually aren’t actually “full” metal jacketed, but simply have a copper jacket covering the top of the projectile. Military FMJ ammunition is completely covered by a copper jacket (as per the Hague Conventions), which uses a more involved process than traditional civilian ammunition (but doesn’t alter the lethality of the rounds).
FMJ ammunition is manufactured so that the bottom of the original cup of copper becomes the tip of the bullet, producing a continuous jacket of copper over the top of the round. However, most civilian ammunition leaves the base of the lead core uncovered, as illustrated with the bullet on the left in the above images (the ones with the three bullets side by side).
FMJ ammunition is cheap to produce, and therefore is the traditional choice for use on the firing range. The uniform and aerodynamic design of the projectile also makes it the ideal choice for long range precision shooting. However, that streamlined design means that it’s also more likely to penetrate a living target (like a human or an animal) and keep going out the other side, possibly injuring people further downrange and leaving only a small wound in the target. Therefore, for home defense and hunting it’s not advised to use FMJ ammunition.
There are a couple variations of FMJ ammunition that can be recognized by their designations:
  • Round Nose (RN) — The tip of the bullet is simply rounded in a spherical shape, not particularly aerodynamic. Used mostly in handgun ammunition and older rifle ammunition.
  • Boat Tail (BT) — The rear of the bullet is tapered to give it a more aerodynamic profile. This is common in “match” grade rifle ammunition and long range target ammo.
FMJ ammo is the “default” ammunition style, and the only one where the jacket is “drawn” from the tip. Every other projectile uses a jacket that is “drawn” from the base, and the tip is usually designed to perform some sort of function.

Open Tip (OTM)

OTM, c Nick Leghorn
With FMJ bullets, the bottom of the cup becomes the tip of the bullet. With “0pen tip” bullets, the opposite is true — the bottom of the cup is the bottom of the bullet. While this covers more of the lead core than the FMJ projectile, it leaves an opening at the tip of the bullet where the jacket was drawn together. Many people mistake this for “hollow point” ammunition, but the point is too small to work that way.
Open tip bullets are preferred by long distance shooters as the manufacturing process is more consistent than with FMJ projectiles, leading to higher quality bullets and better performance at long distance. These projectiles are often referred to as “OTM” or “Open Tip Match” to indicate that they are held to a higher standard than regular ammunition.
Due to the construction of the projectiles, open tip bullets perform nearly identically to FMJ projectiles.

Hollow Point (HP)

HP, c Nick Leghorn
For self defense or hunting, hollow point bullets are the way to go. Following the same general manufacturing process as the “open tip” bullets, these projectiles feature an exaggerated opening at the front of the bullet. The idea is that this opening will force the projectile to expand upon impact with a target, dumping all of the energy of that round and creating a massive wound. However, that gaping hole in the front of the bullet also creates an immense amount of drag and negatively impacts the long range capabilities.
Hallow hollow? (courtesy
Gun control advocates have successfully branded hollow point rounds as “cop killer” bullets in a couple states and have implemented legislation banning their use based on the claim that they are in fact “armor piercing.” However, as we have tested and proven, that’s not the case.

Hollow point ammo is the favorite choice for police officers and those who carry a concealed weapon for one simple reason: when they hit something, they stop. They don’t keep going like FMJ rounds can and injure people on the other side of the target.

Soft Point (SP)

SP, c Nick Leghorn
While hollow point ammunition is great for handgun rounds, when you’re hunting at longer ranges with a rifle you need a round  with better ballistic properties. One of the first attempts to make a projectile with the accuracy of a FMJ bullet and the “terminal ballistics” (how well it does when it hits a target) of a HP round was the “soft point” bullet.
The main difference between a soft point bullet and an open tip bullet is that with the SP, some of the lead core is protruding from the front of the round. This gives the bullet a more aerodynamic shape than the OTM bullets, and also has a tendency to flatten the projectile when it hits a target. The bullets don’t open up as dramatically as a HP round, but it’s still better than nothing. Especially where HP rounds are illegal.
But if you’re looking for a really good hunting round for your rifle, there’s something far better out there than a soft point bullet.

Ballistic Tip

BT, c Nick Leghorn
How do you get the benefits of a hollow point with the long range accuracy of a FMJ? By adding a small piece of plastic. “Ballistic tip” bullets feature an exaggerated opening in the tip of the copper jacket to allow the bullet to expand upon impact, but that hole is covered by a cone shaped piece of plastic that allows the bullet to perform as if it were a FMJ. It’s a pretty nifty design, and one that I use to great effect in my hunting ammunition. I used a ballistic tip bullet to bring down a deer on opening day of the last hunting season.

Other Bullet Types

While a lead core is the standard for bullet construction, there are some other interesting designs that are purpose built for specific roles. Here are a few:

  • Frangible — These bullets are made out of compressed granules of copper, and are designed to shatter upon impact with a hard surface. They are used mainly as training ammunition in shoot houses, where over-penetration is a serious concern.
  • Steel Core / Armor Piercing — The lead core is replaced with a solid dart shaped chunk of steel, designed to pierce body armor and some light skinned vehicles. This is the standard M855 5.56 NATO ammunition. This can ruin steel targets, and cause ricochet hazards if used improperly.
  • Tracer — A chemical is painted onto the projectile that burns as the round flies downrange. This allows shooters to see where their bullet flies, but also keeps burning after the projectile lands and can start fires.

The Chemistry of a Bullet

A gunman pulls the trigger and a bullet flies out the barrel in a split second. So the question is, how? What goes on in that very short period of time when the cartridge is hit to when the bullet leaves the barrel? To understand this we have to get down to the basics.

 In order for the shot to exit the barrel there must be a force exerted, this force is seen in Newton’s second low of motion, “When a body is acted upon by a constant force, the resulting acceleration is inversely proportional to the mass of the body and is directly proportional to the applied force.” The force that is used to expel the shot from the barrel is achieved through the use of gunpowder. Gunpowder is the propellant used and at a homogeneous mixture of “KNO3 at 74.0%, sulfur at 10.4%, and charcoal at 15.6%,” it is very flammable (23, Rinker). But this is just a portion of the material used, because in order for the gunpowder to light a primer must be used. 

When the firing pin of the rifle hits the center of the case compressor (the extended bump at the back of the cartridge), it will ignite the primer which will then ignite the powder when the “flame passes through vents in the anvil”(19, Rinker). Primers used today consist mainly of “lead styphnate” and, depending on the manufacturer, a mixture of some of the following; “TNT, lead or copper sulphocyanide, lead peroxide, sulfur, tetryl, barium peroxide, and barium nitrate” (19, Rinker). The gunpowder, as a propellant, has “chemical energy” which is converted to move the projectile down the barrel. 

    This conversion involves three steps; chemically the propellant “converts or decomposes almost completely into a gas.” Thermodynamically the energy is “changed into heat which in turn creates motion-power,” and physically the “hot gas pushes the projectile, [then] it reacts to the friction and creates a [sic] recoil” that will force the rifle up and back against the shooter(21, Rinker). Once this process has occurred, it will cause a buildup of a great amount of pressure behind the bullet due to the expansion of the gases. This gas will propel the bullet down the rifled interior of the barrel, which give the bullet spin, and out into the air.
Collection G.Pavan