Author Topic: More on Terminal Ballistics  (Read 379 times)

Alan

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More on Terminal Ballistics
« on: June 09, 2019, 03:07:33 PM »
I found a used copy of Gunshot Wounds, Second Edition, on Amazon. It was written by Vincent J.M. Di Maio. Much of the new data was supplied by Vernon J. Geberth, a well-known forensic consultant, and former Homicide Commander for the New York City, Police Department.

This second addition was Copyrighted in 1999, so it is a bit out of date in two distinct areas of interest to members of the Guild; Airguns, air rifles, and PCP versions of same. But that fact is not the subject of this dissertation. It will take a few paragraphs to explain this enigma.

First, it is interesting to note, that Di Maio differentiates between airguns and air rifles; the former is assumed to be a smooth bore, the latter with some sort of rifling. For most of us, the terms are synonymous. Nor surprising that he doesn’t mention PCP powered weapons at all, since the original text was written in the mid 1990s.

Perhaps more significant, is his differentiation between (powder) handgun and rifle wounds. The main reason stated is that most handgun rounds are subsonic, and most rifle rounds, supersonic. To bring this a little closer to home, the velocity of the vast majority of pellet-firing airguns are subsonic!

This raises many issues, but the most profound one for me, was his findings (with respect to bullet lethality) between the various types of bullets (round nose, flat nose, hollow point, etc.). To cut to the chase, there is little difference in lethality between the various types of bullets at subsonic velocities, while there is a large difference at supersonic velocities. Not to sound egotistical, but I discovered this all on my own, based solely on my hunting experience, both airguns and power burners.

I’ll go out on a limb here, and make a pat statement. At subsonic velocities, Round nosed pellets cause more severe wounds, than hollow point pellets, or those with so-called ballistic tips, at extended distances. At what distance their lethality diverges, has more to do with the initial muzzle velocity than any other factor. This is borne out by Di Maio’s vast autopsic and crime scene experiences.

I should mention at this point, that lethality differences between the various shapes at subsonic velocities is small, when they strike a major organ. When they don’t strike a major organ, what lethality differences they have isn’t evident in most cases. This is why I am convinced that two holes (projectile passthrough) are better than one. As John Schaefer, better know as Fr. Frog (https://www.frfrogspad.com) states (sic), …the more holes to let blood out and air in, the better!

Another issue which needs to be mentioned here, is accuracy. Round nosed pellets have the advantage in long range accuracy vs. any other design. This fact echoes most airgun shooters’ experiences as well.

Travis Mundon, a.k.a. Bullfrog, recently brought up another aspect which needs to be mentioned. Here’s his exact text, and the link to it (http://airgunguild.com/alan's-corner/terminal-ballistics-of-pellets/):

I agree that round nose probably has the superior terminal ballistics, but for different reasons. My take, after killing a lot of larger game, is that the primary damage comes from the pellet's skirt cutting the flesh in a 360 cut as the pellet flies and spins thru. If I'm correct, that would explain while non-deforming 31 gn, .25 Barracudas and 81 gn .357 JSBs can be so deadly on lung shots. Neither pellet deforms in any significant way and offers superior penetration to softer pellets that deform as they pass. After shooting rigid pellets like that into ballistics gel, the boat-prop wound channel I get seems consistent with the skirt cutting as it goes.

I doubted this premise until recently. Even though I didn’t take high school biology, I know enough to do a minor autopsy. When I see (long shot) exit wounds shaped like the profile of a pellet, with the skirt area appearing shredded in comparison to the head area, I’m convinced. At shorter ranges, this doesn’t occur as often. I have to assume the pellet is less stable as it slows in velocity.

And speaking of slowing down. Here is an excerpt from this web site: (http://shoot-on.com/supersonic-vs-subsonic/)

Very little in life comes without a cost, and subsonic ammo does have its limitations. To start with, the maximum effective range of subsonic loads is usually limited to about 100 yds. That’s because subsonic ammo’s low velocity gives it a rainbow-like trajectory and makes it very susceptible to wind drift. Low velocity also seriously limits bullet energy because bullet energy increases as the square of the velocity. Unless specifically designed to expand at subsonic velocities, bullets travelling at subsonic speeds generally don’t have enough energy to expand well, and this limits their ability to transfer energy to the target. This has the potential to seriously limit stopping power. Therefore, the best way to make a subsonic bullet effective at neutralizing a target is through precise placement and deep penetration. The need for penetration is one reason why subsonic ammo is normally loaded with bullets that are heavy for their caliber.

And then there is this excerpt from this web site: (https://www.fieldandstream.com/articles/hunting/2016/04/the-pros-and-cons-of-subsonic-cartridges)

Speaking of which, rimfires are where subsonics really shine. A standard .22 LR load delivers around 1200 fps and 140 foot-pounds of energy at the muzzle. The typical subsonic .22 LR offers around 1050 and 100, respectively, a negligible difference to any rabbit. So while the energy to cleanly kill small game remains, the downrange crack vanishes. And as smallbore competitors know, subsonic .22 LRs are more accurate than supersonic .22s because they exhibit 37 percent less wind deflection due to the disproportional increase of air resistance near the sound barrier. When subsonic .22 LR ammo and a suppressor are combined, you’ve got a whisper-quiet, deadly accurate small-game firearm.

These excerpts contradict one another to some extent, and as air gunners, we know where the real truth lies, if you’ll excuse the pun!

Aside from the wind drift issue, I take exception to the last sentence in the first excerpt for this reason. If the projectile in question is a passthrough, it really doesn’t matter how much the projectile weights. And personally, of all of the sub-sonic ammo I’ve purchased over the years, I’ve never seen any loaded with heavier than normal bullet weights. In fact, it is usually the other way around; lighter than normal bullets.

JSB will soon be offering their Hades pellets in .25 caliber. Although round-nosed, their nose designs does have dimples, for lack of a better word. Based on the .22 caliber results from users, they do provide superior killing power, than standard, round-nosed pellets. Users have also touted their killing power. But what they haven’t reported, is their (Hades Pellets) long-range accuracy. We’ll just have to wait for the results.


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Alan

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Gerard

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Re: More on Terminal Ballistics
« Reply #1 on: June 09, 2019, 10:13:47 PM »
Ted did some accuracy testing with the Hades pellets in .22".


Finishes up saying when they become commonly available, "run, don't walk." Seems he's genuinely excited about both precision and potential for small game expansion.
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Alan

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Re: More on Terminal Ballistics
« Reply #2 on: June 10, 2019, 04:28:07 AM »
I find it interesting, Ted's mention of passthrough. I get passthroughs even with my 397 shooting 7.8 grain pellets through the heads of squirrels, even at 30 yards! I can't remember hitting any game under about 50 pounds, that my .25 caliber, 45 FPE, round-nosed pellet didn't pass through (two holes are better than one?).

And, he only shot at 50 yards. I can get almost any pellet to shoot through my Cobra at 50 yards. But at 75 and beyond, only the round-nosed ones group well. It is at these extended distances I'm focusing on.
  • Roswell, New Mexico
Alan

I have an Omega compressor. If you're a fellow Guild member, and you pass through Roswell, NM, I'll fill your portable tank as a courtesy.

Gerard

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Re: More on Terminal Ballistics
« Reply #3 on: June 10, 2019, 09:11:36 AM »
If 7.8gr you're talking .177", so yeah, I used to get passthrough with that calibre even at 5fpe on squirrels at 10 yards. That's with a head shot from the side halfway between ear hole and eye. But in .22" using 18gr JSB domed I don't get passthrough at similarly close range at 10fpe. Just a lot of blood on the impact side. If it's a bit further out I go to my 20fpe .22" and sure, it'll go straight through from the side. So I usually try to wait for the squirrel to face me, then send the pellet through the forehead and down into the body - most of these shots are from slightly above them so that angle works out. I grab the airgun suitable for the shot. In my efforts several years ago with .177" at lower power I found that wadcutters and Predator Polymags were about the same for not passing through. Domes did go through so I eventually abandoned them.

I prefer to avoid passthrough with squirrels where I use between 10fpe and 23fpe now (and rats, where I use 10fpe or 5fpe depending on range) because I'd rather avoid loud pellet impacts on fences and other yard objects which amplify such a sound. Dirt makes no difference, but only about 1/3 of my shots on rodents are against a dirt backdrop. Neighbours would be annoyed/freaked out if I was making a lot of noisy impacts on wood, so I try to manage my shots such that the pellets for the most part stay in the critter while doing the job adequately. Just got another Eastern Grey (they're mostly the black mutation out here as the guy who introduced them here 95 years ago had a preference for black ones aesthetically) from about 8 yards, about 9fpe at point of impact. Went for the heart shot which I usually don't, as this one was on top of a fence with me looking down on it at about 30 degrees from the third floor porch, and I wanted it to jump into our yard for easy collection. A head shot at that angle would likely have triggered a backflip and a more difficult retrieval from a neighbour's yard. Went exactly as hoped, falling just inside our yard and kicking until the lights went out in about 4 seconds. JSB 18gr pellet went through, as the chest is softer than the head, but only just, not leaving a mark on the fence. About a 2lb male:

« Last Edit: June 10, 2019, 02:20:08 PM by Gerard »
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