October 05, 2022
By Dave Emary
In most Modern ventures, technology and performance are closely related. That statement certainly applies to the shooting-sports industry. During the last 30 years, there has been a persistant push to improve products and provide the consumer with the best performance possible. The availability of monolithic, i.e., “solid,” copper bullets is now prevalent.
Randy Brooks, the retired former owner and CEO of Barnes Bullets, was the catalyst for the American hunter’s current demand for monolithic bullets. Brooks bought Barnes Bullets in the mid-1980s, and he turned a failing company into a mainstay. The product that cemented the company’s resurgence and current standing was the monolithic (i.e., “mono”)-copper X-Bullet.
Brooks, as most people in the industry, is an avid sportsman and hunter. He was well aware of the limitations and inconsistent performance of cup-and-lead-core jacketed bullets because his passion was to hunt large, dangerous game. Bullet performance and reliability were a serious issue for him. On an Alaskan bear hunt in 1985, Brooks had an idea for a bullet that would not have a jacket or lead core, and it would provide more reliable and consistent terminal performance in game. He went to work and developed the design and basic manufacturing process for this bullet. He killed a bear with it in 1986.
Brooks spent two more years perfecting his bullet and understanding the production process before deciding to introduce the X-Bullet in 1989. The concept evolved into an extensive line of mono-copper bullets from Barnes in several different styles for different applications. Other bullet and ammunition manufacturers have since followed suit, introducing their own mono-copper bullets. Let’s take a look at how these bullets work, the offerings and differences.
The Ins & Outs
Mono-bullet manufacturing starts with a cylinder of copper alloy. The metallurgy of the copper alloy used is important because it has a substantial impact on the specifics of the design, manufacturing process and the performance of the final product. As the copper cylinder is formed into the bullet’s shape, the amount of work at each stage of the process is carefully controlled. Overworking the copper creates a material that is hard and brittle, which does not flow and petal back as we’d expect. Instead, such bullets fracture. There is a considerable amount of expertise and finesse that goes into producing mono-copper bullets.
The first step is to form the base of the bullet. Even if the bullet is designed to have a flat base, the edges of the heel have to be radiused to aid loading into the neck of a cartridge case. If the bullet is designed with a boattail, the cylinder of copper is forced into a boattail die, which forms the desired shape.
Now comes the part where the process and tooling designs must be well thought out. All expanding mono bullets have a deep cavity that is formed in the nose. This cavity is where the hydrostatic pressure from impact forces the copper petals to begin opening and flowing back. Depending on velocity, a pretty flower-type shape results from the expansion. The cavities are formed in several stages by progressively longer and larger-diameter punches. Many of the bullet designs will have a final punch that is a long, tapered obelisk shape forced into the cavity. This creates sharp corners in the top of the cavity that are the fracture lines along which the copper petals tear apart when they roll back and expand. This feature can clearly be seen in the cutaway of Hornady’s new CX bullet, immediately below the tip. The shape and taper of the cavity and the resulting thickness of the copper petals determine how fast the petals expand and roll back. This is one big advantage of monolithic bullets over lead core bullets. In lead core bullets the jacket is there to allow the bullet to be fired at high velocities without fouling the bore with lead. The jacket is also there to support the lead and slow down the expansion so it doesn’t quickly turn into a frisbee and produce a very large but shallow wound cavity. The final step is to force the copper core into a die that forms the nose, and then the pressure-relief grooves are cut in a process.
Mono-copper bullets are much better at controlling the rate of expansion due to of the higher strength of the copper and the relatively thick petals. Mono bullets expand and transfer energy at a slower rate than softer lead-core bullets. Because of this, they produce a deeper maximum-diameter wound cavity than lead-core bullets, and they offer more penetration. Mono bullets lose almost no weight during expansion and provide more penetration than you would think for the weight. My rule of thumb has been to add 25 percent to the weight of the mono bullet, and that’s about the weight of a comparable lead-core bullet. Many of these bullet designs will penetrate near 30 inches from a rifle, even at higher velocities. This is significantly better than lead-core bullet performance. Don’t shy away from mono bullets because they seem light in weight.
There is no utopia or free lunch. Copper is about 30 percent lower in density than lead. Mono bullets would have to be very long to match the weights of the heavy-for-caliber lead-core bullets. With rifling twist rates standardized for nearly every caliber, there are limits to the length and weight that these bullets can be made to stabilize. They are generally at the lighter end of the spectrum of bullet weights for caliber, yet very long. The long-for-weight bullets have much more case intrusion than lead bullets, and this can limit powder choices for top performance. Barnes Bullets and Hornady have started offering heavy-for-caliber monolithic bullets for specialty applications. They are also popular with the newer and faster-twist cartridges.
However, mono bullets usually don’t shoot as accurately as lead, cup-and-core bullets. This is significant because there isn’t as much flexibility in the manufacturing of them. That is not to say you will get poor accuracy from mono bullets; I’m simply suggesting that you shouldn’t expect the level of accuracy you might expect from the best cup-and-core bullets. My 6.5 Creedmoor with good cup-and-core hunting bullets will shoot .75 minute of angle (MOA) all day. With mono bullets, accuracy is more like 1.1 to 1.2 MOA. Certainly, this is plenty of accuracy for the ranges these bullets should be used at.
This explanation brings us to identify another limitation of mono bullets: They are harder and tougher than lead-core bullets. They will stop expanding effectively at shorter ranges and higher retained velocities than a cup-and-core bullet. I wouldn’t count on a whole lot of expansion from a mono bullet that is carrying less than 2,000 feet-per-second of retained velocity. The tipped mono bullets will extend this expansion velocity range about 100 fps slower, and it will increase the BC a little to retain more velocity at longer ranges. Hornady’s CX line of mono bullets has some design features that extend its performance.
The first generation of Barnes X-Bullets got some bad press for excessive copper fouling. With further development and refinement of alloys (and multiple pressure relief grooves), this problem was eliminated. Current mono bullets don’t seriously foul any worse than cup-and-core bullets. The reason for the grooves on the newer mono bullets is to allow somewhere for the copper to flow when it is being engraved by the rifling, and to compensate for the long bearing surface that these bullets have. This helps to reduce copper fouling. These multiple grooves come at a price, though: Each groove lowers the ballistic coefficient (BC) of the design .010 to .015 points, depending on the bullet and specific groove shape. Hornady’s CX line uses radiused grooves instead of square-shouldered grooves. This approach reduces the BC loss to very small numbers.
Barnes Bullets offer component bullets and the same in loaded ammunition. Calibers from .22 to .458 are made for rifle loads, and pistol chamberings from .357- to .50-caliber are also available.
Triple Shock (TSX) is essentially Randy Brooks’ original X-Bullet with three pressure-relief grooves. These bullets are a hollowpoint with a short boattail. The boattail doesn’t provide an aerodynamic advantage, it just aids loading and reduces the bearing surface.
Tipped Triple Shock (Tipped TSX) is exactly what it sounds like: The TSX bullet with a polymer tip. The tip improves the BC a bit, helps retain velocity and improves low-velocity expansion. These bullets provide expansion in the 1,900 fps range for retained velocity.
The Long-Range X Bullet (LRX) is a line of longer and heavier bullets that carry a polymer tip and a longer, more effective boattail. Refer to barnesbullets.com for twist-rate limitations that some of these bullets have. They are designed for long-range performance and feature higher weights, a polymer tip and improved aerodynamic design.
TAC-TX is a line optimized for law enforcement and military applications. These bullets are light for caliber and have large polymer tips. The light weight, high muzzle velocity and large tip provide rapid expansion and limits over-penetration for tactical applications. These bullets also perform well against urban barriers.
TAC-XP is a bullet with a large hollowpoint designed for pistol calibers. These bullets are an excellent choice for handgun hunting.
Expander MZ is a saboted hollowpoint line of muzzleloading bullets. The design and shape is nearly the same as bullets in the TAC-XP line, just longer and heavier.
Spitfire TMZ is a saboted, tipped boattail bullet that offers high BC and improved extended-range performance for the muzzleloading hunter.
Federal Trophy Copper is a polymer-tipped bullet with multiple pressure-relief grooves. It’s a short boattail for loading convenience. Federal bullets are only available in loaded ammunition though. They offer a very large range of weights and calibers from .223 Remington to .338 Lapua to 12- and 20-gauge slug loads. The .280 Ackley Improved has recently been added to the lineup.
Hornady CX and MonoFlex bullets are available as both component bullets and in loaded ammunition. Bullet options span from .243 to .45 caliber, and a 12-gauge slug load is available with a 300-grain MonoFlex bullet.
Hornady recently upgraded its GMX line of mono bullets with the CX line. Bullet weights are essentially the same as the former GMX, but the CX features the Heat Shield tip instead of the older Acetel polymer tips. The high-tech plastic improves the BC of the bullets by preventing tip melting and deformation at high velocities. Again, Hornady has gone to a radiused groove on the CX bullets, which substantially reduces drag and improves BC. The CX line also offers 6mm, 6.5mm and .30-caliber bullets that are heavier with long ogives and long boattails. These bullets compete well by weight with lead-core VLD long-range bullets. These are the highest BC mono bullets available. Beware of BC claims that seem too good to be true. They probably are. I have a high confidence in Barnes Bullets’ and Hornady’s claimed BCs since they are generated using radar; others are often estimated or determined over short ranges at high velocities.
Hornady also offers several MonoFlex (MFX) bullets designed for the .30-30 Winchester and .45-70 Gov’t. The .45-70 bullet is also offered in a muzzleloading sabot for muzzleloaders. These bullets feature a pointed flex-tip for tubular magazine safety and high a BC. I can personally attest to their performance. I took a 1,600-pound buffalo with the 140-grain MFX bullet using a vintage Model 94. The bullet completely penetrated the massive chest of the buffalo and destroyed the heart in its travel.
Nosler E-Tip Expansion Tip (E-Tip) bullets are available as component bullets and in loaded ammunition. The Nosler E-Tip is a polymer-tipped, short, boattail bullet with a single pressure-relief groove. The boattail serves more as a loading aid than an aerodynamic enhancement. A range of calibers and weights are available from .22 to .375.
Winchester Copper Impact is only available in loaded ammunition. Several popular cartridges are available including 6.5 Creedmoor, .350 Legend, as well as 12- and 20-gauge slug loads.
Winchester has shortened the “Deer Season XP Copper Impact” name to “Copper Impact.” It has begun to expand offerings, also. Copper Impact is a specialized bullet with a large polymer tip, single pressure-relief groove, and an effective boattail to reduce bearing surface and provide better BC. Bullet weights are on the light- to mid-weight range. With large tips and a large cavity in the core for rapid expansion and maximum energy transfer, these are limited in penetration and best for thin-skinned game such as deer and antelope.
Winchester has begun making heavy-for-caliber bullets in this line, including a .30-caliber, 180-grain bullet, intended for big game. The Copper Impact line is available in a range of calibers as well as 20- and 12-gauge slugs.
It would be difficult to find an expanding bullet type that offers greater penetration (including bone penetration) than mono bullets. Copper solids provide the hunter more flexibility for poor presentation shots than most lead core bullets. Consider them for your next hunt. Caution: When hunting with mono bullets, avoid targeting an animal lined up with one behind it. It’s not unheard of to take two animals with one shot. Mono bullets penetrate!
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