Projectile Tech 101: A two-part series (part 2) / Sgt. James Spitzer (Retired)

An Expanding Bullet serves two distinct functions.

.40 S&W cartridge next to expanded hollow point bullet. Photo courtesy of Oleg Volk on Wikipedia

.40 S&W cartridge next to expanded hollow point bullet. Photo courtesy of Oleg Volk on Wikipedia

The first function is to create a larger wound track, thereby inflicting more damage to the central nervous system, the cardiovascular system or the muscular/skeletal structure of the unlucky recipient.  The empty space trailing behind a bullet is known as the wound cavity.  Wound cavities come in two varieties; the permanent and the temporary.

The Permanent Wound Cavity is simply the result of the bullet drilling its way through the tissue it encounters. Largely dependant on the projectiles’ diameter, it is practically the only tangible effect of low velocity cartridges such as handgun ammunition.  An expanding bullet can increase the diameter of the permanent wound cavity by 200% over a similar non-expanding Bullet.

With high velocity cartridges, such as rifle ammunition, the permanent wound cavity is eclipsed by the Temporary Wound Cavity. This is the result of the projectiles’ kinetic energy explosively forcing the tissue away from the bullets path in a radial fashion like a large wake behind a speedboat.  It lasts only a few milliseconds, but is many, many times the diameter of the permanent wound cavity.  It quickly closes up due to the elastic nature of the tissue, but the shock wave effect has already caused extensive trauma to any veins, arteries, nerves, and even bones in the effected area.  It is the most devastating effect of high velocity projectiles, and more closely linked to bullet velocity than diameter.

The second function of an Expanding Bullet is to expend as much of the projectiles’ kinetic energy as possible in a shorter wound track.  Any kinetic energy remaining in the bullet after it has fully penetrated the intended target is wasted, or worse, can proceed on to strike an unintended target such as an innocent bystander.  Expanding Bullets are a classic contradiction; they are both deadlier and safer at the same time.

The expansion of a bullet is generally achieved by deforming the nose of the bullet to a mushroom type shape upon contact with the target.  The method by which it produces this expansion may differ slightly, as you will see, but always requires a threshold velocity to make it possible.  Most literature states a minimum of 900 feet per second to expand under the best of circumstances.

Historically, the Jacketed Soft Point (JSP) Bullet (originally known as the Dum-Dum Bullet) was the first successful Expanding Bullet.  With the advent of smokeless powder in the late 1800s, velocities increased, and bullets began to get smaller and lighter. The designers needed to have a metal jacket surrounding the lead bullet to handle the increased velocity and pressure inside the barrel. The first full metal jacket bullets tended to penetrate straight through a target and produce little damage. This led to the development of the Jacketed Soft Point (JSP) Bullet at the British Arsenal in Dum-Dum, near Calcutta in 1894. These bullets simply had the copper jacket trimmed away at the nose to expose the soft metal core. On contact with the victim, the soft core would flatten out and produce the effects discussed earlier. First used at the battle of Omdurman in 1898, they were outlawed for military use by the Hague Convention in 1899 (often confused with the later Geneva Conventions). However, the Hague Convention has never applied to Civilian and/or Police use of expanding bullets.  Jacketed Soft Point (JSP) Bullets are very common in hunting, defense and police applications.

Hollow Point Bullets expand more readily than Jacketed Soft Point (JSP) Bullets due to the hollow point cavity, which is simply a hole pressed or drilled into the nose of the Bullet.  It concentrates the pressure of any liquid or tissue in the nose, hydraulically forcing the metal outward to create a larger diameter projectile.  The Lead Hollow Point Bullet (LHP) is the most basic form of Hollow Point Bullet, and is still seen occasionally.

Jacketed Hollow Point (JHP) Bullets are covered in a coating of harder metal such as copper or brass to increase the bullets’ strength and to prevent lead fouling of the barrel.  They are the most common type of bullet for any purpose other than target shooting. They typically come with a flashy name and a patented design.  Examples would include; Golden Saber, Extreme Shock, XTP, Gold Dot, Star Fire, and on and on.  The Marketing Departments of Ammo Companies often walk a fine line when naming their products, such as the case of the famed Black Talon bullet.  It was simply too well marketed, and developed a legendary mystique about it that had shooters lining up, but also drew the ire of most anti-gun groups.  Having ‘Black’ in the name also produced some uncomfortable racial overtones.  Having learned their lesson, Winchester modified the color of the bullet from black to plain copper, and changed the name to the more innocuous ‘Fail Safe’, and then later to ‘Ranger SXT’.  Everyone seems to be happy with it now, even though it is essentially the same bullet. The Hydra-Shok is a variant of the Jacketed Hollow Point Bullet in that it has a small (but patented) lead post inside the hollow point cavity which is supposed to create more reliable expansion.  Reliable expansion is the key word when comparing Jacketed Hollow Point Bullets.  It is not uncommon for a Hollow Point Bullet to go through thick clothing such as a leather jacket, and for the Hollow Point Cavity to become plugged with those fibers, turning it for all practical purposes into a non-expanding bullet such as a Full Metal Jacket.

Many rifle shooters also claim that JHP bullets can have greater inherent accuracy due to the bullets center of mass being shifted slightly to the rear, but others disagree.

Frangible Bullets, which are designed to disintegrate on impact into tiny particles, fit the loose definition of an Expanding Bullet.  These were once referred to as ‘Gallery Bullets’ which are used in shooting galleries to minimize the possibility of a wayward bullet fragment injuring a customer.  A true Frangible Bullet turns to a dust like consistency after impact, but one interesting variant is the Glaser Safety Slug. They basically start with a traditional Jacketed Hollow Point Bullet, but remove the Lead Bullet Core and replace it with an equal amount of tiny lead birdshot pellets and then seal the nose with a thin layer of plastic.  On impact, the jacket opens and dumps its load of birdshot pellets onto the wound track, which individually have very little kinetic energy, thus minimizing the chance of bullet over-penetration and the risk to innocent bystanders. Hence the name ‘Safety Slug’.

In 1994  Signature Products, a Huntsville AL based firm , announced plans to market a Frangible Bullet that they called the ‘Black Rhino’ which they claimed was so lethal that it would produce a ‘non-survivable wound’.  The national media quickly rallied against it, Congress shook their fists in outrage and made plans to ban it, and gun control groups generally lost their minds.  Prototypes were tested, but in the end, the Black Rhino Bullet was never manufactured, earning it the title of ‘the most deadly bullet that never was’.  Here’s what I find fascinating; once you peel away the hype, you find that the infamous ‘Black Rhino Bullet’ was virtually identical to the ‘Glaser Safety Slug’ in every possible respect except for the way that it was marketed.  The design is so similar that if they had actually gone into production, Glaser probably could have sued them for patent infringement.  It amazes me how much difference a little spin can make.

Exploding Bullets are about as common as California Condors, but are nevertheless always popping up on TV.  Marketed under the names ‘Exploder’ and ‘Devastator’, they were basically Jacketed Hollow Point Bullets with a pistol primer and small amount of shock sensitive explosive such as lead azide in the hollow point cavity.  In theory, the primer was supposed to ignite the explosive on impact and fragment the bullet to produce a larger wound cavity.   In practice, they just simply didn’t explode unless you hit a concrete wall at an angle of 89 to 91 degrees on a warm day with a tailwind.  If they did detonate, the effect was difficult to distinguish from that of a regular Jacketed Hollow Point Bullet.  In 1981 John Hinkley used Devastators when he attempted to assassinate Ronald Reagan.  Although he seriously injured a lot of people, including the President, none of the six shots actually detonated. While Exploding Bullets had Hollywood and the ‘gun store commando’ types lining up with their tails wagging, they were pretty much all hype and no substance.  They haven’t been manufactured in years and while they were banned in a couple of states, they still surface occasionally as a collector’s item, which is the only real value they ever had.

Sgt. James Spitzer spent 37 years working as an Independent Consultant in the Forensic Discipline of Firearms Identification.  He now resides in Auckland, New Zealand and is best known for a high profile case that garnered national attention in 2003 in which he performed forensic examinations and subsequent courtroom testimony as Solicitor General’s Witness in a trial that led to the conviction of controversial Kiwi poacher Whitey “Chickenbone” Carter.

(The Killer Nashville Guest Blog series is coordinated by KN Executive Director Beth Terrell (  To be a part of this series, contact Beth at


About Clay Stafford

Clay Stafford is an author / filmmaker ( and founder of Killer Nashville ( As a writer himself, he has over 1.5 million copies of his own books in print in over 14 languages. Stafford’s latest projects are the feature documentary “One of the Miracles” ( and the music CD “XO” ( A champion of writers, Publishers Weekly has identified Stafford as playing “an essential role in defining which books become bestsellers” throughout “the nation’s book culture.” (PW 6/10/13)
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