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Critical Defense vs. Critical Duty: Clearing up confusion over Hornady ammunition

These two lines of ammunition are designed to address very different needs


These two lines of ammunition are designed to address very different needs.

Photo/Hornady Manufacturing Co

As an avid student of ballistics, I’m often asked what the difference is between the Critical Defense and Critical Duty lines of ammunition from Hornady. The similar sounding names help to establish these products as market siblings, but sometimes confuse the average buyer.

That’s a problem, because these two lines of ammunition are designed to address very different needs, and a department purchasing agent or individual officer who’s considering them needs to understand how they’re different from each other.

To start, we need to understand that in 1988 the FBI established a new protocol for testing law enforcement handgun ammunition that quickly became the industry standard, because it was so widely adopted as the yardstick for measuring bullet performance.

The yardstick
The protocol is a series of six standardized tests, where bullets are fired into 10 percent ballistic gelatin, according to detailed procedures. In the first of those tests, the bullets are fired into a bare gelatin block, but in the remaining five tests, the bullets must pass through specified barriers before entering the blocks, including heavy clothing, steel, wallboard, plywood, and automobile glass. Properties such as penetration depth, recovered diameter, and retained weight are measured to compare bullets against each other, and against FBI-desired standards.

FBI standards require ammunition designed for law enforcement is able to penetrate gel between 12 and 18 inches in each of the six tests, and the industry has responded with products that do. From an engineering standpoint, it’s a tough task to design a bullet that will perform all these jobs acceptably well, and some trade-offs are involved — you may wind up sacrificing performance on one test to ensure you’ll pass another.

For example, if you want a bullet that can pass the difficult auto glass test, you might end up with a design that penetrates more deeply than desired in bare gelatin.

Critical Defense
The important thing to know about Hornady’s Critical Defense ammunition is that it was not designed to pass the full FBI protocol, because it was never envisioned as law enforcement-duty ammunition for service-size pistols. Instead, it was designed for defensive situations where no intermediate barrier (other than clothing) was involved, and it was assumed that it would be fired from compact carry guns with short barrels.

Those short barrels rob velocity and decrease energy, which often leads to under-expansion and over-penetration in soft targets. They also increase muzzle flash, so the Hornady engineers had to address these concerns in the design of the product.

Critical Defense is optimized for short barrel performance in the bare gelatin and heavy clothing stages of the FBI protocol, with an emphasis on avoiding over-penetration. This makes the ammunition useful to armed citizens for concealed carry and home defense and to law enforcement officers in situations where barriers are not a likely concern, such as off-duty carry, back up guns, and possibly some undercover operations.

The Flex Tip eXpanding (FTX) bullet developed for Critical Defense ammunition looks like a traditional Jacketed Hollow Point (JHP) bullet whose cavity has been filled with a polymer plug. When the FTX bullet strikes a target, the polymer plug gets compressed and produces outward force on the inside walls of the cavity, which opens up the bullet for controlled expansion. An advantage of this kind of design is that the cavity is not susceptible to getting plugged with debris (such as clothing fibers) that might retard hydrostatic expansion of the bullet — a common issue with traditional, open-cavity JHPs.

Critical Duty
After the success of the Critical Defense bullet in the commercial market, Hornady turned their attention back toward the full FBI protocol and the development of a suitable law enforcement bullet that would excel in all the tests, including barriers. The result was the Critical Duty “FlexLock” bullet.

The Critical Duty FlexLock bullet shares a similar external appearance with the Critical Defense FTX bullet due to the use of a similar, compressible plug in the nose cavity, but it’s a different bullet on the inside. To begin with, the bullet jacket is heavier to provide increased strength. Additionally, the heavier-for-caliber lead core is mechanically locked to the jacket by means of a tongue and groove type arrangement. As a result, the heavier bullet expands but maintains enough integrity to punch through tough barriers without the core and jacket separating from each other, as they often do in traditional “cup and core” designs.

The result is a barrier-resistant bullet that still offers suitable expansion and penetration — an ideal match for duty conditions.

Defense vs. Duty
To compare the two, it’s useful to look at how these bullets perform in the heavy clothing test. Fired from a short 3-inch barrel, the Critical Defense FTX 115 grain 9 mm bullet penetrates 11.25 inches, expands to 0.55 inches diameter, and retains 100 percent of its weight:


Critical Defense 9 mm 115 grain FTX, Heavy Clothing. (Photo/Hornady Manufacturing Co.)

In comparison, when fired from a service-length 4.5-inch barrel, the Critical Duty FlexLock 135 grain 9 mm bullet penetrates 15.25 inches, expands to 0.56 inches diameter, and also retains 100 percent of its weight:


Critical Duty 9 mm 135 grain FlexLock, Heavy Clothing. (Photo/Hornady Manufacturing Co.)

You can see how the heavier FlexLock bullet, designed for barrier penetration, goes deeper into the gel than the lighter weight FTX. This extra energy is needed for performance in the barrier tests that the FTX is not designed to pass, such as steel or auto glass:


Critical Duty 9 mm 135 grain FlexLock, Steel. (Photo/Hornady Manufacturing Co.)


Critical Duty 9 mm 135 grain FlexLock, Auto Glass. (Photo/Hornady Manufacturing Co.)

Choose wisely
So, what we have here are two different bullets for two different tasks. You’ll need to choose the appropriate tool for the appropriate job. Critical Defense is for short barrel guns where barrier penetration is not important and reducing over-penetration risk is. Critical Duty is for LE missions where you would like a “barrier blind” bullet that will still expand and penetrate after punching through intermediate obstacles.

Don’t let the similar sounding names confuse you. Take the time to make the right choice, and be safe out there

Mike Wood is the son of a 30-year California Highway Patrolman and the author of “Newhall Shooting: A Tactical Analysis,” the highly-acclaimed study of the 1970 California Highway Patrol gunfight in Newhall, California. Mike is an Honor Graduate of the United States Air Force Academy, a graduate of the US Army Airborne School, and a retired US Air Force Lieutenant Colonel with over 26 years of service. He’s a National Rifle Association (NRA) Law Enforcement Division-certified firearms instructor, senior editor at, and has been a featured guest on the Excellence In Training Academy and American Warrior Society podcasts, as well as several radio and television programs. He’s grateful for the opportunity to serve and learn from the men and women of law enforcement.