How to Select a Hunting Cartridge, Part 3: Terms, Conditions, and Fine Print.

by Scott Fletcher

“It’s always something”. – David Tooley

Part 2 introduced a simple empiricism that estimates the weight of a non-dangerous game animal that can be efficiently harvested based solely on a cartridge’s expanding-bullet weight and impact velocity, regardless of a specific brand-name bullet. Four notes are presented that provide guidance for the empiricism’s use.

The intent of this article is to identify and discuss the primary limitations of the empiricism in the context of the four guidance notes presented in Part 2. Even if these limitations are premeditatively taken into account, use of the empiricism may not result in a recovered non-dangerous game animal of the estimated weight implied by the calculation. “Your mileage may vary”.    

The following note discussions will introduce valid terminal performance concepts that can be used with the empiricism to assess how specific bullets could likely perform based on their general design features and the typical materials used in their construction, independent of a manufacturer and a specific bullet’s brand name. Such a general design-and-materials categorization is called a generic design. A bullet’s generic design can be a general indicator of its key terminal performance metric values, and can be used as guidance to select a bullet considered necessary to meet specific hunt objectives.

Note 1) is akin to telling folks to “stay out of the orchard and don’t eat the apples”. (Somebody wrote about that a long time ago.) The reason is the bullet used to hunt dangerous game must have a generic design intended to produce specific performance objectives, as will be explained using Photo 1 and Photo 2. Quite simply, using just “any” bullet with a weight appropriate for the intended animal is not valid for dangerous game, and its use can be the posterchild for potentially lethal consequences.

Photo 1, furnished by Andrew Mackay of Australian Outfitters, shows an Australian “scrub bull” found in the Northern Territory. Scrub bulls are feral cattle of various species considered to be a nuisance and are hunted accordingly. Depending upon the species, gender, and habitat, they can weigh from about 1100 to 2640 pounds (500-1200 kg). Like all bulls, they have a nasty disposition when wounded and are considered dangerous. Mr. Mackay uses a 375 H&H to hunt these animals, a chambering consistent with dangerous game.

If a maximum shot distance of about 150 yards (137 m) is assumed, tinkering with the empiricism and the various bullet weights available in a .375 caliber could result in 350-grain candidates being considered, as shown in Photo 2. Left-to-right: 375 H&H cases loaded with a 350-grain Woodleigh Weldcore protected point and a 350-grain Sierra Match King with a hand-installed poly tip to consistently initiate expansion.

The EGW for the Woodleigh is about 1900 pounds (864 kg), and the EGW for the Sierra is about 2100 pounds (955 kg). The reason for the Sierra’s greater EGW is because of its substantially greater BC (.810 vs .400) and a greater muzzle velocity (2425 fps vs 2360 fps) due to the reduced bearing length inherent in its boat-tail design.

Disregarding the generic designs of the bullets shown in Photo 2, all the “numbers” indicate the Sierra should be a slam-dunk selection. However, disregarding the generic design of each bullet when applied to this hunting scenario could literally be a “fatal flaw”.

The Sierra is a match bullet constructed with a “thin” and a metallurgically “soft”, untapered jacket as well as a metallurgically “soft” lead core. These comparatively soft materials will quickly and easily expand, reducing the bullet’s ability to penetrate through any tissue or bone. As with all match bullets, the jacket is not bonded to the core, and thus creates a discontinuity (plane of weakness). This discontinuity does not allow the jacket to essentially reinforce the core to create a combined-strength material to better resist the bullet’s deformation caused by both initial impact and post-impact penetration. This discontinuity also contributes to rapid and extensive expansion, further contributing to poor penetration.

In addition to the Sierra’s thin, soft, and unbonded components, its poly tip will initiate very rapid expansion upon impact. On a broadside shot, the rapid initial expansion coupled with the combined design and material features indicate that the Sierra may not penetrate sufficiently to completely breach the boiler room (thoracic cavity) in spite of its significant weight. Should the shot be low and hit the shoulder joint, the joint would likely completely stop its penetration, with any wounding only produced from an indeterminate volume of bone shards spraying into the nearside lung. Bottom line: using the Sierra could open a 2000-pound (910 kg) can of whup-a$$ with no effective remedy.

The Woodleigh has a metallurgically “hard”, comparatively thicker jacket bonded to a metallurgically “hard” core. These stouter, bonded materials significantly reduce the rate and the extent at which the Woodleigh expands, thus enhancing its ability to penetrate. Furthermore, the jacket completely encompasses the lead at the tip to retard the degree of initial expansion upon impact, further enhancing its ability to penetrate through thicker, more tenacious shoulder muscle and bone. These combined design and material features can be expected to result in a complete breach of an animal’s boiler room on a broadside shot on the shoulder, with potentially enough bullet structural integrity to breach a shoulder joint, if encountered.

Note 2) is directly related to how the bullet factor (BF) value of 7.5 in the empiricism was derived, described in detail in eBook Chapter 19. The animal weight and cartridge data obtained from Aagaard’s book resulted in a factor of about 8.6; from Boddington’s book about 7.7; and from Robertson’s book about 6.5. The average of these BF factors is about 7.5, the one used in the empiricism. The BF factor of 8.6 is about 15% greater than the 7.5 average, and the BF factor of 6.5 is about 15% less. This range of bullet factors is the basis for the potential 15% variation in EGW identified in Note 2).

The Guppy analytical model and bullet gel testing had not been completed at the time when the empiricism was derived. As a consequence, there was no appreciation/recognition of bullets with exemplary Guppy-metric values nor the potential qualitative relationship between their terminal performance characteristics and generic design features. Aagaard customarily used bullets of a generic design widely acknowledged to “lose weight” during penetration, while Robertson tends to favor bullets that retain weight. As demonstrated during gel testing and with skinning-shed autopsy data presented in the 2023 management hunt report, bullet weight loss contributes to increasing wound cavity volume. Greater wound cavity volume customarily obtained from bullets typically used by Aagaard could potentially explain the greater BF value associated with his animal data. Regardless of the anecdotal relationship suggested by the Roberston and Aagaard data, bullets with exemplary Guppy-metric values, as indicated by gel testing, do exist and their terminal performance can be qualitatively related to their generic design.

Note 3) recognizes that two of the three data sets used to link the calculation to animal weight had shot impacts on the shoulder to take out the heart as well as lungs. Data in the 2023 management hunt report clearly show that an increase in wound cavity volume results in a shorter time to death. The typical North American and African management hunt practice of placing shots behind the shoulder to only affect the animal’s lungs will reduce the total volume of vital-organ wounding produced. The reduction of total vital-organ wounding with a lung-only shot increases the animal travel distance, and thus increases the risk of an unrecovered animal. The degree of increased risk of an unrecovered animal cannot be quantified, but is not zero.

The previous discussion associated with Note 1) indicates a bullet’s generic design can affect its ability to effectively/consistently penetrate thicker, more tenacious shoulder tissue and bone in order to breach an animal’s boiler room. A bullet’s generic design is equally important if shot placement is intended to only affect the lungs, as the primary terminal performance objective shifts from primarily penetration to maxing out wound cavity volume.

Shots to the lungs only require penetration through significantly thinner tissue and less substantive rib bones. In this application, a bullet with a generic design that results in rapid and extensive (explosive) expansion to max out wound cavity volume is highly preferable to a bullet with a generic design intended to produce performance primarily emphasizing penetration. Such explosive terminal performance would likely significantly increase the lung-only wound volume, and consequently reduce the travel distance.

A bullet with a generic design intended to only enhance penetration would be a poor choice for a lung-only application. Personal gel testing has shown the wound cavity volume produced by “penetrator” bullets is anemic compared to the wound cavity volume produced both by bullets with a generic design intended to produce a balance between penetration and wound cavity volume, and by bullets with a generic design intended to primarily produce a large wound cavity volume. If the animal in the Note 1) discussion had been a non-dangerous, 2000-pound (910 kg) eland (Photo 3) that was to be taken with a lung shot on a management hunt, the poly-tipped Sierra would be preferrable to the Woodleigh because of its likely superior wound cavity volume.

The previous discussion of how the bullet’s generic design affects its likely terminal performance relative to the kill-shot’s aim point on the animal can be used to assess how (or if) the plus-or-minus 15% factor identified in Note 2) can be strategically applied. The bullet’s generic design can indicate a primary performance intent that can be generalized in three ways: penetration (“penetrator”), a balance between penetration and wound cavity production (“balanced”), or wound cavity production (“expander”). If the shot is on the shoulder, increasing the calculated EGW by 15% is reasonable for a balance bullet; the calculated value is reasonable for a penetrator bullet; and decreasing the calculated value by 15% is reasonable for an expander bullet. If the shot is on the lungs, increasing the calculated EGW by 15% is reasonable for an expander bullet; the calculated value is reasonable for a balanced bullet; and decreasing the calculated value by 15% is reasonable for a penetrator bullet. The default EGW for bullets with an obscure/unknown generic design is the directly calculated value.

Note 4) represents what manufacturers could do on behalf of their customers to better-define the capabilities of their products. Quite simply, a bullet’s terminal performance depends on both its generic design and its impact velocity.

An expanding hunting bullet’s generic design and impact velocity determine its terminal performance metric values by controlling both the degree and the rate of its deformation/expansion. The terminal performance metric values of every bullet, no matter what its generic design, change with changes in its impact velocity. For example, a reduction in impact velocity can transform expander bullets into ones producing a reasonable balance between expansion and penetration, and can transform penetrator bullets into ones acting like solids because the impact stress is insufficient to cause any expansion. Because of these changes in terminal performance metric values, there is only a limited range of impact velocities over which each bullet can be expected to produce terminal performance that is consistent and in general accordance with a manufacturer’s design intent. Gel testing, as described in eBook Chapter 10, can identify a reasonable range of impact velocities in which relatively consistent performance can be expected.  

At the time this article is written, only one manufacturer, Woodleigh Bullets, furnishes a published impact-velocity recommendation for each of its bullets. Anecdotal information can be found on the internet that confirms/justifies these published impact velocity ranges. Limited personal gel testing results and field performance on the zebra management hunt also substantiate the recommended impact velocity range for its 30-caliber, 200-grain Weldcore protected point.

Speculative impact velocity ranges based on a bullet’s generic design are presented in eBook Chapter 13, Chapter 14, Chapter 15, Chapter 16, and Chapter 17. These ranges are based on limited personal gel testing results and practitioner accounts published on the internet.

A worked example problem that uses the empiricism and the terminal performance concepts just discussed, including impact velocity considerations, is presented in sections 8.0 through 9.0 of the 2023 management hunt report. This example problem presents the cartridge and multiple bullet-selection process used successfully on the hunt.

The empiricism presented reasonably estimates the weight of a non-dangerous game animal that can be efficiently harvested based solely on a cartridge’s expanding-bullet weight and impact velocity, regardless of a specific brand-name bullet. Although its input is simplistic, its answer has a basis in observed reality and sound terminal performance concepts supported by applicable material properties and engineering mechanics. When the empiricism is used in accordance with the guidance presented in this three-part series of articles, its result is judged to have enough conservatism to allow a reasonable degree of surety for a pass-fail judgement as well as sufficient precision to indicate when options should be considered, including abandoning the initial, preferred cartridge.