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I'm sure some of y'all have heard of H.I.T.S. (Hornady Index of Terminal Standards). There are other indexes of course noted in the link at the bottom of the quoted article.

Since a common topic is what bullet/cartridge combo is best for a specific use, this might help. Often it's about handgun ammo for SD purposes. The Hornady calculator provides some general guidance, particularly if we assume that the avg. person could be defined as "Medium Game". ;) It does not consider bullet design (FMJ, JHP, etc.) but only the factors noted below.

Here's the calculator: HITS calculator - Hornady Manufacturing, Inc



The most recent attempt to quantify terminal performance in simple terms has been put forward by Hornady in the form of an online calculator. Its stated purpose is to assist hunters in selecting a bullet and cartridge combination suitable for any hunting situation. After a little experimentation I derived the terms of the calculation, which is given below:

HITS = Bullet Weight2 / Bullet Diameter2 / 7000 x Impact Velocity / 100

Alternatively, recognizing that some of the terms constitute the sectional density:

HITS = Bullet Weight x Sectional Density x Impact Velocity / 100
Having calculated this value, one then compares the score to four categories:

  • 500 or Below -- Small game weighing less than 50 lbs
  • 501 to 900 -- Medium game with a body weight of 50 to 300 lbs (e.g., deer, black bear and caribou)
  • 901 to 1500 -- Large and heavy, but non-dangerous game weighing from 300 to 2000 lbs (e.g., elk, moose, African plains game, bison, etc)
  • 1501 or Above -- Dangerous game of any weight (including, for example, big cats)
This system bears a strong resemblance to the Optimum Game Weight calculation, but differs in important respects. While, unavoidably, any calculation would lead to splitting hairs and comparisons between cartridges, the HITS system only indicates the general class of game animal suitable for that load. Hornady makes no advertisement that the values correspond to the relative capabilities of the loads in anything more precise than the four general categories. Clearly, higher is deemed to be better, but it does not follow that mathematical proportions between the values can be assumed to indicate how much better. In other words, a HITS of 1500 does not indicate that the load is twice as powerful as a load with a HITS score of 750. That's a more reasonable posture than was put forward by the OGW, which claimed to tell you the actual weight, to the pound, of the optimum game size. Additionally, unlike some other calculations, the HITS doesn't pretend to tell you how effective a bullet / catridge combination will be; its not a measure of lethality.

While I don't endorse any of these quick calculations as rendering some deeper insight into the actual mechanics of terminal ballistics, the HITS methodology does tend to push the user toward solutions which are known to work better: higher sectional density and heavier bullet weight for heavier game. It doesn't include the unfortunate bias of velocity that the OGW creates, nor the bullet diameter bias of the TKO. For the most part, its a conservative result.

Perusing the tabulated HITS for all the Hornady ammunition, at first nothing leaps out as an obvious case of mathematical mischief. None of the .223 Remington loads is judged to be suitable for medium game, not even the 75 grain loads. None of the 6 mm or .257 caliber loads is judged to be acceptable for elk and other large game. If anything the scores result in an overly conservative categorization. Goodness knows how many elk have fallen to the .32 Winchester Special and .30-30 Winchester, despite their sub-900 HITS scores. But a little conservatism these days is not necessarily a bad thing.

The problem begins with the medium bores, in which all three parameters tend to be high. The .338 Winchester Magnum with a 225 grain bullet is judged suitable for dangerous game, which might be true depending on the game in mind (think leopards, lions or bears) and the bullet chosen. However, the Hornady Super Shock Tip shown in the table, a rapidly expanding and lightly constructed, boat-tailed bullet, would not be a good choice for any of these game animals. It might even be a fatal choice. Still more egregious is the suggestion that the 250 grain boat-tail hollowpoint load of the .338 Lapua might be a dangerous game load. Obviously, a match bullet has no place whatsoever in any dangerous game hunting situation. On the other hand, none of the big-bore lever gun loads of the .405 Winchester, .444 Marlin, .45-70 Government or .450 Marlin are judged minimally acceptable for dangerous game, including the big cats or bears, and these would all be first rate for that role even if we leave aside the debate over their utility against heavy, thick-skinned dangerous game.

Once beyond medium bores that possess enough velocity to score as dangerous game loads and the lever gun loads lacking enough to qualify, things return to expectation, which is to say that the truly big bores are all judged to be suitable choices for dangerous game. No surprises there.

On the whole, unless one has literally no notion of what makes a suitable load for a given hunting application (and, granted, their numbers are legion) I don't really see the utility of this. But then again, maybe I am missing the forest for the trees. Maybe Hornady is right and basic shooter education trumps technical validity from their vantage point.

The worst outcome of this sort of calculation to my mind is the impression fostered that the performance of a load is largely or even totally independent of the bullet chosen. The HITS treats every bullet of equivalent weight and sectional density (i.e., caliber) the same. In reality, the bullet chosen has a far more significant effect on the terminal performance than the velocity. Across a wide velocity spread the wound pattern will be similar for a given bullet of good design, but the differences between a monolithic solid, a bonded core hunting bullet and a varmint or match bullet of equal weight and caliber would be dramatic. Hornady does speak to the applicability of the bullet to the purpose in general terms, but its clear that their desire to use this new tool and apply it without further elaboration to their current line of ammunition outweighs any concern for misuse of their products. A simple statement in a footnote indicating which loads do not qualify as dangerous game loads (in fact why are match loads even shown here at all?) would suffice, without impugning the validity of what the HITS provides, at least in the mind of the target consumer.

Terminal Ballistics


 
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