Fluid Transfer Monolithic Bullets: Next Gen Defensive Cartridge?

Since the middle of the 20th century, the defensive projectile has undergone significant advancements. Bullet profile, bonding, and material are just a few of the broad range of projectile design and manufacturing advancements. Regardless of these improvements, the vast majority of defensive projectiles remain hollow or soft points. After years of slight changes, it seemed hollow point bullets reached the pinnacle of defensive handgun cartridges. However, monolithic bullets—specifically fluid transfer monolithic bullets—have garnered some well-deserved attention.

If fluid transfer monolithic (FTM) bullets are a foreign concept to you, that’s okay. Up until about two months ago, I understood little of what makes FTM bullets so unique and effective. After some research, long discussions with the folks at Underwood Ammo, and a little testing of my own, here’s everything to get you started on how and why FTM bullets could be the next generation of defensive projectiles.

What are monolithic bullets?

Monolithic bullets are single-material projectiles commonly made of copper. They aren’t exactly new technology. For the last few decades, solid copper projectiles have expanded into the defensive and hunting ammunition market. I’ve hunted with solid copper Barnes TSX bullets for years with consistent and dramatic results.

However, the all-copper composition of monolithic bullets presents a few challenges. First, copper doesn’t have the same density as all-lead or copper-jacketed lead-core projectiles. As a result, copper bullets tend to have a different profile from traditional lead-copper projectiles. In the past, copper bullets also tended to cause more copper fouling, especially in rifle barrels. With advancements in alloys, excessive copper fouling seems to be less of a complaint.

While monolithic projectiles have proven reliable, some felt there was something beyond traditional hollow point, soft point, or ballistic tip designs. From this passionate curiosity and innovation, fluid transfer monolithic bullets became a reality.

Fluid Transfer Monolithic Bullets

Fluid transfer monolithic (FTM) bullets represent a significant deviation from expanding defensive projectiles. Before delving into FTM projectiles, we need to understand how traditional expanding projectiles work.

How do fluid transfer monolithic bullets differ from hollow points?

The common hollow point projectile utilizes a conical cavity at the front of the projectile to produce expansion. When a semi-compressible fluid (e.g., blood, tissue, organs, etc.) enters the projectile’s cavity at a high enough velocity, the compressed fluid causes bullet expansion. As the bullet expands, it transfers energy from the bullet into the target’s cavity, generating permanent and temporary wound channels. Ideally, this energy transfer results in target incapacitation.

FTM bullets operate on a different principle from hollow points. FTM projectiles produce direct energy transfer from projectile to target without bullet expansion or deformation. An FTM projectile deletes the familiar hollow point cavity in favor of a bullet profile with fluted channels and a flat point. This projectile evokes comparisons to a Phillips head screwdriver.

How do fluid transfer monolithic bullets work?

From my experience and investigation, FTM projectiles produce impressive permanent wound channels. But if they don’t expand, how do they work? Bear with me as we delve into some physics.

A bullet’s energy is calculated based on its velocity and mass. Heavier bullets (larger mass) increase energy linearly, while higher velocity increases energy exponentially. However, the biggest issue with projectile performance isn’t necessarily energy at impact. Rather, the problem surrounds a projectile’s efficient energy transfer into the target. For example, one hollow point and one full metal jacket (FMJ) 147-grain 9mm bullet both produce the same energy. However, since the hollow point expands, it transfers energy into a target more effectively than the FMJ.

This brings us to the two largest types of energy associated with a projectile: rotational and linear. When a bullet exits the barrel, it rotates during its trajectory. For reference, a 9mm from a 1:9 twist Glock barrel spins at approximately 88,000 RPM. While hollow points have long capitalized on a projectile’s linear energy, FTM projectiles capitalize on the projectile’s linear and rotational energy. Consequently, FTM bullets represent a radical shift in how we define a defensive projectile.

To work properly, FTM bullets utilize flutes in the bullet’s nose to transfer energy into the target since it’s spinning at tens of thousands of RPM. The nose flutes of FTM bullets produce direct energy transfer from bullet to target without projectile expansion. By not expanding, less energy is lost from the bullet to the target; rather, it’s translated directly into the target. As a result, FTM bullets should produce larger permanent and temporary wound channels with greater penetration. If you’re like me, you need to see it to believe it. Luckily, I have some initial results I’m happy to share here.

Seeing is Believing: Hollow Point vs FTM Bullet Performance

While I can bore you with numbers and scientific terminology, seeing is believing. With the aid of a chronograph and homemade ballistic gelatin calibrated to FBI standards, I tested a modern hollow point cartridge against an FTM projectile. The modern hollow point selected was the Hornady Critical Duty 135-grain 9mm +P. While Critical Duty is not a traditional hollow point, it functions on the same principles as most hollow points with the aid of a flexible polymer insert. Underwood Ammo generously provided their Xtreme Defender 90-grain 9mm +P for the FTM projectile.

From 10 feet away, I shot two ballistic gelatin blocks with a 4.5-inch barreled Glock 17. Both cartridges provided impressive permanent and temporary wound channels. Hornady advertises a muzzle velocity from a 4-inch barrel at 1,010 fps. However, it produced 1,131 fps through the Glock 17’s longer barrel. The lighter Underwood Ammo cartridge advertises 1,475 fps at the muzzle but produces 1,527 fps on the chronograph.

The Hornady penetrated 14 inches, while the Underwood penetrated an impressive 17.5 inches. After recovering the projectiles, the Hornady offering weighed 129 grains, which I attribute to the polymer tip lost during expansion. The Underwood projectile remained in one piece and almost appeared capable of being reloaded with a 90-grain recovered weight.

Permanent Wound Channel

Wound channels are divided into two categories: permanent and temporary. Permanent wound channels remain after the projectile passes through or stops within the target. Temporary wound channels occur due to the projectile’s immediate energy transfer into the target. In reviewing the Hornady hollow point and Underwood fluid FTM’s performance, there was a clear winner in both wound channel categories.

The monolithic Underwood cartridge produced an impressive permanent wound channel diameter compared to the Hornady. Initially, the Hornady appears to have a larger permanent wound channel of 1.75 inches at approximately two to three inches into the gelatin block. However, the Underwood cartridge produced a two-inch wound channel that expanded to over three inches between approximately two and seven inches of penetration. The two wound channels contrasted significantly with each other when measured by sustained, permanent wound channel width over penetration distance.

A side-by-side comparison of the permanent wound channels shows a distinct difference between how these cartridges perform. The hollow point cartridge dumped a significant amount of energy into the target as it encountered the gelatin, expanded, and transferred energy. As a result, the hollow point produced a rapidly increasing permanent wound channel upon entry, with the width tapering off relatively quickly. Conversely, the monolithic projectile entered the gelatin and produced a wide permanent wound channel that expanded to its maximum width through the block before tapering off. While I can probably work through the math to provide a number for the overall wound channel expansion area through the first block, the images are telling. The monolithic bullet generated an obviously longer and wider permanent wound cavity compared to the hollow point.

Temporary Wound Channel Comparison

A temporary wound channel can provide insight into a projectile’s energy transfer into a target. However, it’s not a good indicator of a bullet’s mystical “stopping power.” In this case, the target was 22 inches of ballistic gelatin. While the permanent wound channel illustrated a profound difference between hollow point and fluid transfer monolithic bullets, the images of the temporary wound channel left me in awe.

The 90-grain Underwood projectile produced a massive, temporary wound channel throughout the first block. The images indicate the temporary wound channel almost ruptured through the top of the block. The 135-grain Hornady was no slouch and produced a significant temporary wound channel. However, when placed side-by-side, the difference was undeniable.

Before the gelatin testing, several peers were intrigued by Underwood Ammo cartridges. After sending them images of the temporary and permanent wound channels, their intrigue evolved into newfound respect. Needless to say, several wanted more testing before passing a final opinion. However, I suspect some of that desire for more testing may be just to see more of the FTM bullet’s impressive performance. I absolutely plan to indulge in more in-depth testing at a later date.

The Future of FTM Projectiles

While one test doesn’t determine the future of defensive projectiles, it’s a thought-provoking observation. If you can stand to have or dedicate the time to conduct your own research, you’ll find my impressions and results far from ground-breaking. Rather, they’re just confirmation of the potent effectiveness of FTM projectiles.

So, where do fluid-transfer monolithic projectiles lie in the future of defensive cartridges? While my opinion may ruffle some longstanding dogma, FTM bullets could ultimately revolutionize the future of defensive cartridge design. Hollow points have long been the standard and proven performer, but FTM projectiles stand poised to turn the status quo on its head. Don’t believe me? Try it for yourself, and you might be as intrigued as I am.