How Gel-Test Guppy Metrics Can Be Used to Evaluate an Expanding Hunting Bullet’s Likely Field Performance, Part 6: Context and Summary Conclusions.

By Scott Fletcher

“I’m not crazy; my reality is just different from yours.” – Cheshire Cat from Lewis Carroll’s Alice’s Adventures in Wonderland.

The previous five parts of this article have described how the Guppy-model with its attendant gel-test metrics can be used as a tool to empirically evaluate an expanding hunting bullet’s fundamental field performance objectives of wounding, penetration, and meat preservation. Like any tool, its effective use requires an understanding of its intent, when and how to apply it, and a reasonable expectation of outcome.

The Guppy’s intent is simply to model and empirically predict the reality-based wound observations of Colonel Townsend Whelen, a US Army Ordinance Corps officer who is one of the most highly regarded of all hunters and riflemen. Without benefit of an analytical model or testing, Colonel Whelen simply used his field observations of wounding to produce his empirical conclusions about a bullet’s lethality. Likewise, Christopher Columbus used simple field observations of sails on the horizon to empirically conclude the earth was round. Ol’ Chris was right; it just took a while for technology to catch up and repeated “field reality” to validate his assertion. I believe the Colonel is right; the Guppy model represents the combined technology and testing to both conceptually explain and empirically apply his assertions until technology evolves with a more scientific predictive method.  

The Guppy model is the alternative to “energy” being used to both explain and predict a projectile’s field terminal performance. As indicated by real-world examples presented here that any hunter can relate to, “common sense” says a projectile’s impact energy is not responsible for the wound volume produced.  Furthermore, I can find no technical basis where impact energy has been used to predict a bullet’s field wound volume, penetration, or meat damage. Anyone hell-bent on arguing that point should first find published authoritative field terminal-performance data that validate a predicted result based on impact energy. In the interim, I would suggest fully digesting the reality identified by the bass-ackwards relationships between bullet impact energy and real field wound-volume data presented on Graph 4 and Graph 5 from the 2023 hunt report. The reason the relationships presented on the graphs don’t make any sense can be succinctly summarized using my preferred red-neck techno-speak: a bullet’s impact energy don’t mean jack $#!+. Clear enough?

The nebulous notion of a bullet’s “energy” has considerable mojo. Everybody can mindlessly parrot this single word as the unchallengeable explain-all reason for the “whys” and “hows” of a bullet’s terminal performance, specifics be damned. Its value can be determined by a scientific one-and-done equation that yields a number precise to any place beyond the decimal point. Nuclear bomb-like “energy release” with a magnitude in the thousands causing violent Hammer-of-Thor catastrophic tissue mayhem is seductive to the male ego. The notion of “energy” simply “feels right”, particularly when hunters have been led to believe it produces “shock” that results in instantaneous drop-to-the-shot death. (Real field data say bullet impact energy doesn’t cause drop-to-the-shot death; just read the article found here.)

The Guppy model with its attendant gel testing has “issues”, all considered bad juju. Nobody has heard of it or uses it. It’s “odd” and “complicated”. It incorporates too many unproven/currently unaccepted physiological concepts with too many equations and too many metrics that aren’t directly applied to predicting field performance of interest. Bullet weight loss and mushroom diameter obtained from testing are considered to be nothing more than factoids and not used, contrary to accepted bullet-evaluation practice. The evaluations using Guppy metrics can be characterized as “hand-grenade” analysis, only intended to give answers that are “close enough”. The resulting numbers must be interpreted in terms of what might could be rather than in terms of what will be, always in conflict with what an “equal” sign says is absolutely so. Its implementation requires labor-intensive testing that can cost serious money and calculations that some folks don’t know how to do. Finally, absolutists will argue the resulting metrics are completely bogus because the testing medium is 20% synthetic gel, not the “approved” ordinance gel used by the FBI.

All undeniably true. Such is the fate of any empirical-evaluation model and its metrics when current technology is incapable of precisely and scientifically explaining “the nature of things” or how “stuff” really works. However, no matter how seemingly far-fetched an empirical analysis might appear, its merit depends only on how accurately and consistently it predicts real-world outcomes. Both the likelihood of predictive certainty and the magnitude of any predictive “busts” must be considered to ultimately have reasonable confidence in any empirical evaluation, scientific exactitudes be damned.

Hunt data presented throughout this website preliminarily indicate reasonable certainty of the empirical field-performance predictions made based on Guppy metrics obtained from testing in 20% synthetic gel. There have been no ugly field-performance outliers without reasonable or data-based explanations for their deviation.  

However, there are insufficient data points to realistically say the Guppy model with its attendant gel testing is either an appropriate or inappropriate empirical way to evaluate an expanding bullet’s field terminal performance. What can be said is the gel-test data obtained to date produce Guppy metrics that have empirically predicted reasonable data-proven field outcomes, useful for making informed terminal-performance choices. Additional successful field predictions made with the Guppy-metrics V(ST), L(T), and I(V) are required to achieve the statistical confidence to validate the legitimacy of the Guppy model with its attendant gel testing.

Because the Guppy model is empirical, the field performance predicted by its metrics of V(ST), L(T) and I(V) must always be judged in terms of “likely”. There is no guarantee against an unexpected/disappointing wild-card outcome. However, I know of no other terminal performance analytical method with its attendant tests that provides the surety to remove the word “likely” from any judged terminal-performance outcome.

As applied to non-dangerous game, Guppy metrics obtained from testing in 20% synthetic gel can be reasonably used to compare the likely reality-based wounding, penetration, and meat damage produced by any expanding hunting bullet fired from any cartridge. Based on the data to date, the Guppy model’s predictive metrics likely put hunters who use them on the correct playing field between the foul lines, in position to score an easily-recovered animal.