Impact Expansion Bullets: The Better “Hollow Point”?

The topic of handgun stopping power is immensely popular both online and in print media. I cannot be critical of those who follow the topic as I was once fascinated by it as well. So much so that I made it the subject of my thesis for my master’s degree in criminal justice administration. This effort resulted in a network of people I was able to draw upon to keep track of which rounds/calibers were actually working in the street, and which were not. Over time these folks retired, as did I, but decades of active research proved the “caliber wars” were based more on marketing than post-mortems and, regardless of chambering, bullet size, expansion, and velocity are still only part of the equation. As Dr. Vincent DeMaio, former Texas Medical Examiner, and the author of “Gunshot Wounds,” once said, “It’s where you hit them and how many times you hit them” that really determines handgun incapacitation potential.

Expansion does offer some performance advantages, however. An expanding bullet slows inside the body delivering some energy to surrounding tissues. There’s not hard and fast rule about how much tissue damage bullet expansion creates, but let’s be honest, any amount is a positive if it helps stop a threat. Common sense tells us a bullet that gets bigger has the potential to damage more tissue as it passes. In addition, a bullet that stays in the body does not become a danger, via pass-through, to non-hostiles that may be behind a perpetrator. Think about bullet expansion like this; a round that passes in and out of a target is like an ice pick, little damage done. A bullet that enters, gets bigger and suddenly stops will certainly cause greater damage. At least, that is the way my simple brain thinks of it.

Of course, missed shots are a greater hazard than over-penetrating rounds, but this has always been the case. And keep in mind the bullet that hits the wall next to our attacker nullifies all of the ballistic research that went into its creation. The downside of a bullet that expands and slows is potential lack of penetration, both in the body and through hard objects a threat may use for cover. Motor vehicles are of special interest to law enforcement officers as a high percentage of enforcement activities take place in and around vehicles. Considering the amount of time the average citizen spends in and around cars, and increased risk of transitional spaces, there is also a good chance of a vehicle being involved in any defensive scenario.

Simplistically, a conventional hollow point expands due to what some call a “hydraulic factor” or “fluid physics”, i.e., fluid (blood, urine, fecal matter), wet material (tissue), or other matter enter the bullet’s nose cavity. Due to the forward momentum of the bullet, the material cannot escape backwards. Instead, it presses out against the sides of the cavity and initiates outward expansion. In early hollow point designs, the bullet’s walls usually lost integrity and blew out on one side or the other, if at all. Expansion was seldom a complete mushroom as seen in the lab, when test bullets are fired into consistent tissue simulant. The human body is not a consistent medium. It’s a mixture of hard bone, tough muscle, soft gelatin-like fat, and fluid-filled regions.

Current hollow point technology has solved many previous expansion problems through cavity and jacket designs that allow for consistent expansion of the side walls. Bonding mechanisms have increased penetration through tissue and intermediate barriers. But even as good as current hollow point bullets are, they are still subject to plugging due to solid material clogging the cavity, which can turn the bullet into a conventional round nose projectile that will likely pass though the intended target. While bullet designs like the Federal HST, which expands quite well through barrier materials, have taken this into account, it can still happen.

Years ago, I was invited to the Federal Ammunition plant in Minnesota where I had the opportunity to check out the research and testing going into the company’s Expanding Full Metal Jacket (EFMJ) round, a bullet that would expand via impact instead of the conventional hydraulic factors. EMFJ used a polymer “pill” in the center of the bullet design to create expansion with a solid nose basically compressing the jacket-trapped polymer. While there, I was also permitted to see testing for the projectile that would become the HST. I remember the proto-HST bullet being very impressive, and I am not surprised by how well the design has worked in the street. The EFMJ load was eventually introduced under the Federal Guard Dog self-defense line.

Other companies, too, recognized the potential shortcomings of traditional hollow points, and worked to solve the problem of plugged cavities. Hornady introduced both Critical Defense and Critical Duty loads, and they’ve worked well in a number of documented shootings I am aware of. In truth, the 135-grain 9mm +P Critical Duty load has been an exceptional performer. Critical Duty/Defense is different than EFMJ in that they have more conventional bullet cavities, but they are pre-filled with polymer material that upon impact compresses and pushed outward to initiate and accelerate expansion. While different, they are still dependent on impact to expand or deform.

Speer developed a bullet to FBI specifications that is now known as the “Gold Dot LE II” or “G2.” The bullet looks like a conventional Gold Dot hollow point with a clear elastomer material “protecting” the hollow point cavity. Plugging the cavity appears to be a more reliable expansion method than the polymer pill included in the bullet itself. I gained some hands-on experience when representatives from Speer brought the G2 to the range during the filming of my training video, “Vehicle Combatives.” During that shoot, we were able to conduct a complete battery of bullet and barrier testing for the cameras. In fact, I left very impressed with the G2. Individuals I respect, who have seen the FBI testing of this bullet, were greatly encouraged with one telling me “I have carried a .45 for 20 years, but I just went out and bought a Glock 17 because of what I saw.”

It should be noted that, currently, the FBI is issuing the 135-grain Hornady Critical Duty load, but that does not mean the G2 is dead. Another major federal agency is utilizing an enhanced version of the G2, as are a number of state and local agencies. This loading uses an oxide coated design with a shear ring to break off during glass penetration, making it more consistent when penetrating through auto glass. In addition, a lighter-weight version of the G2 bullet is now available to local police and armed citizens in the 135-grain G2 Carry Gun load. Building upon the law-enforcement proven G2 bullet, Speer has enhanced the design to provide superior feeding and terminal performance for compact concealed handguns. Gold Dot Carry Gun features the original’s exclusive bullet nose design, but instead of a large hollow-point cavity, it has a shallow dish filled with a high-performance elastomer. On impact, the material is forced into specifically engineered internal fissures to start the expansion process. This results in uniform expansion, better separation of the petals, and more consistent penetration across barrier types.

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It should be noted that, due to the superior G2 technology, the EFMJ bullets and Guard Dog line have been discontinued, but the folks at Federal tell me no to be surprised if they come back with enhanced technology in the future.

Am I enthusiastic about impact expanding loads? Not so much by current technology, but by the potential performance that could be built into the bullet design. While at the Federal plant, I had a conversation with several engineers working on the EFMJ project. They ask me to consider a hypothetical bullet that expands only while it is in contact with an external medium. Essentially, the expansion stops when the contact stops. As an example, a bullet that passes through a car window is only in contact with the auto glass for approximately ¼ inch, so, expansion would be minimal. But, if the bullet then struck a perpetrator inside the car, the bullet would resume expanding as it traversed through the bad guy. The extended contact time would theoretically result in a fully expanded bullet. These are interesting ideas!

I’m not sure if impact bullet design is currently perfected, but it is getting closer and closer. Both controlled testing and real-world results bear this out. The current G2 is much improved over the original EFMJ, while Hornady’s Critical Duty load continues to show promising results in actual shootings, expanding well even when passing through intermediate barriers.

While I would not call impact expansion loads “smart bullets,” I do believe they have a strong potential to take the crown for best combative ammo from traditional hollow points. Too, because they largely eliminate fragmentation, it’s worth considering their viability and legality for use by the military. I have been told the Federal EFMJ was used during the Global War on Terror by several special mission units, as well as U.S. Marines in both .40 S&W and 9mm loads. While they may not perform to the level of some well-proven law enforcement hollow points, I was told they were superior to standard NATO Ball loads. I spoke to one Marine who was present when an EFMJ was used to shoot an insurgent with a Beretta 92 pistol and he advised that two rounds took the terrorist out of the fight. “This was a real improvement,” he said, “normally you have to drain the magazine as ball 9mm acts like an ice pick, in and out with little effect.”

Only time will tell if impact expansion ammo will be the next wave of combative ammo, but I, for one, am greatly encouraged.