The Anatomy of a Hunting Bullet

In this day of digital marketing and computer-generated imitations, it can be difficult to sort out what’s real and factual. This problem is further compounded by social media and video platforms where anyone, regardless of their qualifications and experience, can espouse their opinions and thoughts on any topic. I’m not saying that the internet and social media is all bad, but too much of the information is simply opinion, or based on little more than a couple of vague observations or hearsay. 

A recent YouTube video sent to me for comment is a perfect example of this. The person in the video was discussing what made a good hunting bullet and what was important in such a bullet. He said, “The most important thing in a hunting bullet was retained energy,” and he was annoyed with all the recent high ballistic coefficient (BC) hunting bullets being offered. He added, “BC is just a number and really has little relevance to a hunting bullet. Only retained energy matters.” That made me chuckle. 

If you’re going to try and argue that retained energy is all that matters, then how can you separate energy from retained velocity and retained velocity from BC? BC totally dictates what the retained velocity and, therefore, retained energy of a bullet is.

With this in mind, a discussion of the available types of hunting bullets is in order. To cover how they work, where they work and where they stop working.

Mechanics of Expanding Hunting Bullets

What I consider a hunting bullet is a bullet purposely designed to have some level of controlled expansion. An expanding bullet is one that increases its frontal diameter after striking and during penetration of soft tissue. By expanding, these bullets transfer kinetic energy to the target by means of hydrostatic shock and permanent crushing, tearing and destruction of soft tissue. The destruction of soft tissue is fairly easy to envision. It is the hole in the animal you just shot or the meat that is so pulverized that you can’t eat it. 

Hydrostatic shock is something a little harder to envision. A very large percentage of any soft tissue is water. Water, at the impact velocities of bullets, is essentially incompressible and does not want to get out of the way. This sets up a shock wave in the soft tissue, much like the shock wave a supersonic bullet creates in the air around it. This shock travels through adjacent tissue and organs, and can pass through large blood vessels and cause damage to organs quite a distance away. This is the physiological damage that virtually any high-­speed projectile causes. Expanding bullets cause a lot more of it.

There are three overarching types of expanding bullets: Bonded, non-­bonded and monolithic copper alloy. Bonded and non-­bonded designs use a drawn-and-formed copper jacket encapsulating a lead core. In a bonded bullet, the core is bonded to the jacket, usually by some type of soldering process. Because of the process, the lead core usually needs to be pure lead and the copper jacket needs to be nearly pure copper with little, if any, alloying metals or a strong bond will not be formed. Both pure lead and pure copper are significantly softer and not as strong as alloyed lead and copper commonly used in non-­bonded jacketed lead-core bullets. Because of this, bonded bullets will usually have thicker jackets to control expansion of the softer, more easily deformed lead and copper jacket. Non-­bonded bullets usually use gilding metal, which is copper alloyed with about 5 percent zinc, which makes it harder and stronger. Non-­bonded bullets can also use lead alloy with tin or antimony that makes the lead harder and tougher. Most non-­bonded jacketed lead-core bullets have thinner jackets than a bonded bullet because of the harder lead and copper jacket. The advantage of the bonded bullet is that the core and lead will stay together while penetrating, which gives consistent penetration results. Well-­designed non-­bonded bullets usually don’t have jacket separations, but no one can pound on the table and say with a straight face that jacket separation with a non-­bonded bullet can’t occur.

The disadvantage of bonded bullets is that the thicker jacket will not shoot as accurately as thinner-­jacketed non-­bonded bullets. The thicker bonded jacket is more difficult to achieve comparable jacket concentricity when placed next to thinner non-­bonded jackets. If you need a bullet that will give you consistent penetration and not come apart, even if it hits bone, the bonded bullet will work well if you can achieve acceptable accuracy for hunting.

Lead-core jacketed bullets expand due to the forces on the nose of the bullet during impact, which causes the lead to deform, flow backwards and increase the frontal area of the bullet. The lead deformation causes the jacket to open and peel back. The jacket serves two purposes: It protects the gun barrel from fouling with lead, and it supports the lead during expansion, which prevents the lead from being scrubbed off and limiting expanded diameter. The lead hardness, jacket construction and whether or not the bullet has a plastic tip largely determines how fast and to what extent the bullet expands, as well as to how low a velocity it will expand.

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Monolithic copper-­alloy bullets are made of a solid copper alloy, meaning they have no core. These bullets offer almost 100-percent weight retention, deep penetration and very good performance — even if it hits bone. The drawbacks of monolithic bullets are that they can be finicky to get to shoot accurately, and they tend to be very long for the weight.

Monolithic copper-alloy bullets have a hollow cavity in the nose with some designs featuring a plastic tip. Impact forces the bullet nose open or drives the plastic tip into the nose cavity, which forces the nose open. The plastic-tip designs will usually expand at somewhat lower impact velocities than the hollowpoint designs. After the nose is forced open, the bullet is designed to have ogive petals that roll back on themselves, increasing the frontal area of the bullet.

Bullet Types & Performance

Traditional Lead Soft-Point 

These bullets are pretty self-­explanatory. Lead soft points are a jacketed bullet that can be bonded or non-­bonded with an exposed lead point. When these impact, the lead deforms and starts the jacket opening and the lead and jacket continue to deform, which increases the frontal area. These bullets have been around for a long time. Truth is, this bullet type has reliably taken game for more than a century! If you are a traditional hunter and are unlikely to ever take a shot much longer than 300 yards, soft-point bullets will perform well enough. Generally, they will not give much expansion below 2,000 feet per second (fps) retained velocity. This velocity level is well within the retained velocity of normal 100- to 400-yards ranges of a variety of modern hunting cartridges. Non-­bonded soft-point bullets can be quite accurate, though. Examples of soft-point bullets include Barnes’ originals, bonded Federal Fusion, Hornady Spire Point, Remington Core-­Lokt, Sierra Game King and Speer Grand Slam and Hot Core. Nosler Partition bullets are a specialized bullet within this group.

Variants of this bullet type are the round-­nose or flat-­point exposed lead designs commonly used in lever-action rifles and dangerous-game bullets. The larger frontal diameter of these bullets helps to produce the forces causing expansion to offset the low muzzle velocities. Even with the large frontal area, these bullets have limited ranges of expansion capability. Typically, these bullets will not give much expansion far beyond 150 yards from traditional lever-gun cartridges.

Plastic Tipped, Lead Core

As with any lead-core bullet, this design can be bonded or non-­bonded. The plastic tips on impact are forced back into the lead core and jacket forcing the nose of the bullet to open and begin expansion. A plastic tip generally allows the bullet to expand at lower velocities than an exposed lead soft-point bullet. Typically, these bullets will give useable expansion down to velocities of about 1,800 fps retained velocity. The bonded, tipped bullets will usually expand to somewhat lower velocities, 1,500 to ­1,600 fps, because of the softer pure-lead core. Tipped bullets achieve a much smaller meplat diameter than a lead soft point and therefore will have a higher BC for the same weight bullet. This allows the tipped bullet to retain velocity to a longer range, further extending its effective range. Examples of this type of bullet are the Federal Trophy Bonded Tipped, Hornady Interbond and SST, Nosler Accubond and Ballistic Tip, the bonded Swift Scirocco II, Remington Core-­Lokt Tipped and Winchester Ballistic Silvertip and Deer Season.

A newer specialized subset of the tipped bullet are the long-­range designs which are becoming very popular. These bullets are designed to maximize aerodynamics with long sleek ogives and long shallow angle boat tails. Their aerodynamic design along with typically high weight for caliber results in very high BC bullets. Because of the high BC, these bullets will retain velocity for a long time and provide effective expansion to very long ranges. Design features in these bullets allow tip setback at lower velocities where several of these types of bullets will expand, with expansion velocities brought down to 1,600-­1,700 fps or less for bonded types. These bullets are available in bonded and non-­bonded designs. Examples of these bullets are the bonded Federal Terminal Ascent, Hornady ELD-­X and the bonded Nosler ABLR.

Monolithic Copper Alloy

These bullets are available in both hollowpoint and tipped designs. These bullets offer deep and reliable penetration and expansion. They will also survive impact with bone and offer penetration to (and through) vitals. These types of bullets are limited in weight because of the lower-density solid-copper bullet. The bullets are quite long for the weight as compared to a traditional lead-core bullet because of the lower density solid copper. The maximum weight of monolithic bullets is limited because of the long length, and they are available for standard twist rates in commercial rifles. Despite this, these bullets will almost always out-­penetrate a heavier lead-core bullet because they have uniform controlled-expansion and almost 100-percent retained weight.

The drawback of monolithic bullets is they can be difficult to get high levels of accuracy from. They also extend far into the cartridge case, limiting case capacity and making it difficult to get top velocities. These bullets are much harder and stiffer than a lead-core copper-jacketed bullet, so they don’t expand below 1,900 to ­2,000 fps. Examples of these bullet types are the Barnes TSX, Tipped TSX, Hornady GMX and Winchester Deer Season Copper XP.

Barnes also offers the long-range tailored LRX bullet, which features a more aggressive ogive and boattail aerodynamic design, a plastic tip, and about as heavy and long a bullet as can be stabilized in common caliber twist rates. These bullets will not compete with the expansion range capabilities of the lead-core long-range bullets because of their weight and BC limitations, and BC-robbing pressure relief grooves on the body of the bullet. Nonetheless, these bullets offer outstanding terminal performance to distances that the vast majority of hunters would consider outside of their comfortable shooting range.

A Performance Example

As described, different types of bullets will give useful expansion at different velocities. However, this isn’t the only part of effectively and ethically taking game. The rules of thumb of a minimum of 1,000 ft.-­lbs. of energy for deer and 1,500 ft.-­lbs. for elk should be overlayed on top of these minimum expansion velocity ranges. Just because a .224-caliber 62-grain bullet will give some expansion at, say, a velocity of 1,800 fps doesn’t make it a good choice for hunting in this velocity regime with 446 ft.-­lbs. of retained energy. It goes without saying that even the best bullet will not be effective without proper shot placement.

To illustrate the difference in bullet performance, let’s take the .30-­’06 with a number of different 175- to ­180-grain bullet types and see what we would expect as a maximum-effective-range terminal performance shot with each type of bullet. We will assume a muzzle velocity of 2,750 fps. This also assumes we get good enough accuracy from both our rifle and load to hit where we intend to. The expansion threshold velocities are based on the previous discussion of each bullet’s performance. As you can see in the table, there is a wide range of capability in bullets. It all depends on what you want to do in the field and what your expectations are. Make your own chart for your bullet of choice. As long as the maximum expansion range is at ­or greater ­than the energy range you need for the game you’re after, you can have some reassurance that the bullet is within its capabilities. I have to stress again that bullet placement can overwrite all of this.

In Conclusion

The bullet brands and trademarks I mentioned are not all-­inclusive. Do your research and try what looks best for your application. As a hunter, you need to decide what you need in terminal performance and what the outside-of-your-range envelope is. If you are the typical hunter where 300 yards is a long shot, virtually any bullet discussed above will work equally well. With the non-­bonded designs, remember to try to place shots in soft tissue and not shoot through bone if it can be helped. Bonded bullets and monolithic bullets will perform well under almost any circumstance if your rifle will shoot them acceptably accurate.

If you are a long-­range hunter, accuracy becomes an overriding consideration. If you can’t achieve high accuracy levels at long range, and hit where you want, terminal performance doesn’t matter. All the long-­range bullet types discussed above will give effective terminal performance at ranges that require high levels of skill and very good equipment, but you have to have a bullet and load that puts the round where you intend for it to go.

Sound Off

Have a favorite round that you use for hunting that needs some more attention? Let us know by emailing us at GAEDITOR@OUTDOORSG.COM, and use "Sound Off" in the subject line.