Validity of "Power Index Rating?"

[Naphtali]

In Handloader's Digest: Tenth Edition is an article by Ed Matunas, "Loading for maximum PIR" (Power Index Rating) - this being a formula whose calculation is claimed to be an accurate method to identify defensive capability of handgun ammunition. My rule of thumb for my own evaluation is: There's no substitute for cubic inches. I have zero experience with actual need to test my own evaluation, nor have I previously paid any attention to any calculation similar to what PIR claims to do.

Those who have tested such formulae in the real world - I expect there to be very few in this forum - are such things accurate representations of bullet-ammunition "stopping power?"

[tygar]

45s & 308s sure killed better than all the other stuff out there when I was in VN.

[44man]

I stay away from formulas and depend on results only. The .45 ACP can't be beat for defense but some of the 40's are good. The .357 is a known stopper but the nine just has penetration.
Since I deer hunt only I see truth and figures just plain suck. ME figures are not where it is, it is always what the bullet/boolit choice does.

[Blackwater]

You know, you ask a very good question, but it's one that has been debated and cussed and dis-cussed for probably as long as we've had hi vel type loads, which is basically since the advent of the .357's. There are adherents to both sides of the issue and each has their own set of "statistics" that bear out their stance. For me, it's an either-or type proposition - just two ways to get to the same results at least 99% of the time. The arguement is really about that small percentage of variants from the norm, and each also has well founded examples where their stance is superior. I can see both sides, and am very glad we have both. The faster, usually expanding loads facilitate greater range with the handgun without getting into problems posed by the low vel big bullet crowd's choices. The big slow bullet crowd rightly point out that their choice ALWAYS works, at least as to the penetration factor, and that's always a given with their choice. Add in flattened points for additional 'shock' value, and they make a powerful case. The light fast bullet crowd DO acknowledge (usually at least) that things like thick layers of clothing, such as in winter scenarios, CAN occasionally produce less than optimum results with JHP's, etc., which can make their choice less than optimumly effective, and using bullets driven TOO fast CAN limit penetration, which if one meets a 400 lb. brute COULD be rather critical except for brain shots.

Personally, I can go either way, and for me, it basically boils down to the choice between guns that feel good in my hand and that I can use with optimum results. I've settled on a S&W or Ruger .357 4" or the std. 1911 in .45 ACP for my own "optimum" choices, and have great faith in either. The biggest question in the equation is which I can carry most comfortably during all those hours and days and weeks and years when I do NOT need them badly, and that has increasingly become the .45. That's not so much because of any "magic" in the 1911 or the ACP ctg., but because it just fits - the round peg in the round hole for me, if for noone else. Much of the issue really boils down to personal choice, and what degree of compensations and/or discomfort we're willing to put up with in order to "carry." That will always vary from person to person, and there's no real "wrong" answer to it.

However, there really IS a strong correlation between bullet wt., diameter and velocity in what has proven statistically to work "in the streets," and the power factor set forth is a rough approximation of the line between what is reliably effective "in the streets," and what is much more "iffy." The line HAD to be drawn somewhere so the "gamesters" couldn't come in with low recoil guns to gain an edge in times used, and the spot where it's drawn is pretty well generally agreed to be at least a reasonable place to locate the limit. It's low enough to allow calibers with good street records, like the .40 S&W, and high enough to rule out the more iffy calibers like std. loaded 9mm's and .38's. Certainly, calibers as small as .22 LR really HAVE been used to good effect, but in most combat shooting, one aims at the "big middle" of the torso, and a hit there takes more power than a brain shot, obviously, so I think it's pretty well placed, even if it COULD be argued over .... and no doubt WILL be for as long as it's there to BE argued about.

It's probably more "practical" to just shrug our shoulders, take it as it is and respond by making good choices in our guns, and let it go at that. But shooting isn't always about being "practical," and we shooters are a passionate lot, so ... I expect to sit and watch the arguments for a long time to come. It's just the way we shooters do things.

[44man]

The nine has proven to fail in combat. The .45 is still the choice of elite forces. Now we have perps with vests and I will bust a heart even if the boolit does not penetrate. No hope from a .475 or .500.
Of course you would not carry a big gun so what do you do? A .380 or .22? Both can do it but under stress how do you hit just right?
Just read where a perp was shooting at a cop as he ran, then others on the side lines shot at the cop. The cop shot 4 times and missed. The perp tried to jump a fence and got impaled by a post.
Put the Block away and carry a post!
I have friends that will poke the heart out of a deer target from the tree stand but will never, ever hit a deer. Buck fever. Stress on the street is the same. If you do hit, it should count and drop the jerk.

[runfiverun]

the 9 sucks....
I refused to carry the one they tried to foist on me.

[bedbugbilly]

44man - well spoken! In the end, all is "nil" when the adrenaline starts pumping in a very stressful situation. I have seen so many folks debate the best caliber, best bullet and "this is what I would do" . . . and they never consider how they will "react" in a true situation. In reality . . . no one knows and a person will never react in the same way twice. And yes . . . I speak from experience . . . I've been shot at. I've relived that experience many, many times in the past 40 some years and often in the middle of the night. All I know, is that when I went to "hit the ground", it was like "slow motion" and it took forever to "get down". I was not armed at the time, I felt the heat of the bullet on my ear and as the adrenaline kicked in, I couldn't think quick enough (at least that is how I view my situation as I reflect on it). Nobody knows how they will react - as you point out very well with your friend . . shooting paper and targets is a lot different than the actual thing. In reality, it may not make any difference how big your bullet is or how much it expands . . . if you can think fast enough to return fire but can't take the right placement. All you can do is hope, train, practice . . . and pray you are never in the situation where you have to use your weapon.

[olafhardt]

Wagged various 22's around all my life. I have shot at a lot of critters with them. They all died or ran off even the ones I missed. As far as humans go I, just waved it at them and they hightailed. Kids are raised, got more gun buying money and some bigger guns.

[cainttype]

You may find a wealth of info compiled by professionals in forensic pathology by searching "Firearms Tactical Institute wound ballistics"... I can't copy the links to post here, but firearmstatical.com is the site and if you include "wound ballistics" it should bring you to the right spot.
Researching the IWBA, "International Wound Ballistics Association" (an organization including some of the world's leading professional forensic pathologists, it no longer exists to my knowldge), will also provide detailed info on the subject, thoroughly discrediting much of the info accepted as "factual research" in the recent past (and regulary quoted as reference by today's gun literature).

[johniv]

http://www.firearmstactical.com/wound.htm

Here ya go.

[Blackwater]

The real problem with all the "studies" of a medical/scholarly nature is they are almost always aimed at "averages" across the range of human experience in real gunfights, and I don't really trust ANY of them, FULLY. Yeah, they give a general idea of what to expect, but I think a wiser approach is to consider what the WORST case scenario is, and be prepared to deal with it. A 400 lb. methed up gorilla type is going to be a LOT harder to stop than the 140 lb. skinny kid, usually (but not always - human variability DOES cut across physical size). However, the big guy requires a LOT more penetration to GET to the vitals, and little guns like my .380, .32 and .22 won't do it. You HAVE to make a head shot on someone who is in a state of frenzy, and this means you HAVE to keep your head during the incident. If you can't do that, it may well not matter a whole lot WHAT you're carrying. Being able to make the necessary shot at the time when you need to make it is all that stands between you and an early grave if you ever encounter something beyond the "typical" or "average" perp. And they ARE out there.

If I'm about town where there's little liklihood of a serious event, I'll usually carry my little .380, but I have a lifetime of experience behind me of being aware of my surroundings in "civilized" surroundings as well as in the woods, and I don't (or at least haven't yet) folded or hesitated in a tight situtuation. It COULD happen. Even the best and brightest have had occasion to freeze, so I never fool myself that I'm invincible, but that just makes me more determined, and more focused on my surroundings, so that I'm less likely to be surprised. I learned long ago not to take folks I don't know too lightly,and don't assume anything until I'm shown. If for some reason I choose or HAVE to go into a situation where I don't feel comfortable, I'll have my little Kimber Lwt. 4" on me. That'll git-r-done on just about ANYBODY if the shot's placed right, and even with it, a head shot MAY be necessary. It's amazing what some drugs can do to make bad guys seemingly immune from shock, and even if they bleed out, it takes a while, and they've still got time to take you out before they go. With all the drugs out there today, this is more possible than it once was.

Defensive measures are MOST important BEFORE the event occurs, and it takes a LOT more than just buying a gun and ammo, and shooting it a bit. That old phrase, "He who hesitates is lost" applies here better than any of us wish it did, but on the other side, he who shoots TOO soon is probably going to jail for an extended stay, too, so .... ya' gotta' just be prepared mentally to do it right. Too soon or too late, and you're either dead, or may as well be. THIS is the problem that I see few addressing, and it really needs to be dealt with more commonly than it is.

[Naphtali]

So, my basis assumption is pretty much on point: There's no substitute for cubic inches.

[cainttype]

So, my basis assumption is pretty much on point: There's no substitute for cubic inches.


That is the general consensus, combined with enough penetration to punch through the vital zone from any angle. You would need to consider barriers such as fur, clothing, and bones (if an assailant is aiming at you, the bones of the arm will be an external barrier that needs to be considered).
The instantaneous "One shot stop" is only guaranteed with a central nervous system strike, so frontal area and enough penetration to reach the spinal column is a combination that leaves other options wanting. A vital zone hit that eventually bleeds out a threat is no guarantee that you survive the encounter.

[TXGunNut]

Never had to do any real world "testing" but for what it's worth I feel very comfortable with a 45 and feel pretty sure the folks who've looked down a 45 bore didn't enjoy the view.
Energy is easy to measure but very misleading. Penetration is a good thing too, but it's not everything. Outside of a CNS hit a handgun is unlikely to produce a one-stop-shot but I'll generally opt for the biggest caliber I can carry because I feel they transfer energy better and that's what I want a handgun bullet to do.

[Geezer in NH]

IMHO it sold magazine copy's. Same as most of the gun rags used to sell copy.

[rintinglen]

The only serious statistical study I ever saw found that the best correlation between "stopping power" and anything else was with energy, and that was only in the neighborhood of 55%. Momentum, caliber, bullet weight were all lower. The math was good, I don't know about his raw data.
I only have good info on three gunfights wherein a 45 was used--NONE WERE 1 SHOT STOPS. I know of two instances wherein a 357 magnum dropped it's victim with one hit.
What I do not know, is whether that means anything at all. It may be that the 45 is just easier to shoot fast than the heavier recoiling 357. It takes time for someone to fall down, even if they are "dead right there." A fair hand with a 1911 can easily put 3 shots on target in less than a second. It is harder with a .357, though it can be done.

[cainttype]

Thanks for posting the link, johniv.

For those interested, after following the link in post #10 and reading the intent of the site, following the links of reference material at the bottom of the page should be enjoyable... All of the links are relevant to this thread's subject.
Of particular interest is the "Book Review; Street Stoppers..." by Martin L. Fackler, MD.
Researching Dr. Fackler is a worthwhile expense of your time if the "Stopping" ability of any firearm holds any interest to you... Too much bogus misinformation has been dumped on the firearms community for too long.

There are too many "studies" out there that don't pass muster. Maybe the conclusions of real experts, professionals that are highly respected by their peers, should be given a little consideration.

[cainttype]

http://www.firearmstactical.com/streetstoppers.htm

The link to Dr. Fackler's review of what is probably the most quoted reference by gun rags/magazine writers on the subject at hand.
ALL of the other links referred to in my previous post should be interesting to those curious about information that seems unavailable in, or unknown by, the mainstream firearms related press.

[Rick Hodges]

There are no absolutes on stopping power. My family's insurance agent when I was a kid...was stitched diagonally multiple times from his left knee to his right shoulder with a MG-42. He still took out the machine gun that shot him....he lost his leg at the knee, all sorts of internal damage and won a Silver Star in the process. He was not a large man, maybe 5'7" and 140-150 lbs. He wasn't on drugs, and he was scared sh!tless....but multiple hits with a 8x57 Mauser couldn't stop him before he put a grenade into the nest.

[cainttype]

The problem with the usual discussion on "Stopping..." is that real scientific analysis of wound incapacitation traits IS available, but the firearms media seems unaware of most of it. They began supporting erroneous material years ago, and it appears that they are too vested in the misinformation to correct their long-standing support of a false concept.
Is every situation unique?... Of course it is, but better evidence from the scientific community is available on the subject.

The following is an excerpt from yet another scathing review of the gun rag's pet research folly...

Mr. Larry Fletcher, of the Dallas County Institute of Forensic Sciences (formerly the Southwestern Institute of Forensic Sciences), feels that Chapter 5 misrepresents his organization’s findings. He emphatically disagrees with Marshall’s and Sanow’s recommendation of lightweight, high-velocity projectiles such as the 9mm 115gr and 115gr +P+ JHP, .357 Magnum 110gr and 125gr JHP bullets, and .45 ACP 185gr +P JHP bullets. The Dallas County Institute of Forensic Sciences finds the overexpansion and excessive fragmentation exhibited by these bullets results in stretch and crush cavities at too shallow a depth. Mr. Fletcher strongly emphasizes that all of these loads offer inadequate performance for law enforcement use since they exhibit insufficient penetration to consistently reach the major organs and blood vessels in the torso, especially from the transverse and oblique angles commonly encountered in law enforcement shootings. The Dallas County Institute of Forensic Sciences recommends cartridges which offer reasonable penetration and reliable expansion without fragmentation, such as the 9mm 147gr JHP, .40 S&W 180gr JHP, and .45 ACP 230gr JHP.

Here is the link for anyone's curiosity...

http://www.firearmstactical.com/afte.htm

[cainttype]

Maybe this will work...

http://www.firearmstactical.com/afte.htm

[Dan Cash]

A worthwhile read, though a low tech test, is the Thompson-LaGard (sp?) test done back in early 19100s. It resulted in the .45 ACP as service cartridge.

[Blackwater]

As to the ref to 3 guys not being stopped with 1 shot by .45's, I'd be curious to know what kind of bullet wass used in those cases. I know a guy who used to be the chief of the local State Patrol post. His wife was my secretary. He was shot once in the shoulder in that place where no vitals were hit, between top of lungs and all the bones and arteries. He said it was like being hit with a heavy hammer when the bullet struck him. He was a long way from the hospital and nearly bled to death, but survived with little damage after the medics and docs dealt with him. He was shot with hardball.

I'm just thankful we don't have MORE experiences like his to draw from. The Marshall-Sanow data, I believe it is (?) show that the .357 & .45 ACP are about equal in stopping liklihood with a single solid torso hit, and IIRC, the averages are around 9 out of 10 times in street encounter data.

With self defense, the gun's just the TOOL, and it's the carrier that's the "weapon," if you want to call it that, and there's a LOT more to being prepared to defend one's self than just going out and buying a gun and learning to shoot it without hurting anyone else on the range. If you ever have to defend yourself, you'd BETTER be able to keep your head and shoot under pressure. I have little regard for all the comments about how badly "people" shoot when excited. That's THEIR fault! NOT the gun's! Self defense is one of those "do or die" situations, and if we're not prepared IN REALITY, then we just MAY not make it home. In a real "do or die" situation, there are NO excuses, NO second chances, NO time to prepare your mind, you just have to react, and it had BETTER be ENOUGH to do what it takes to go home alive. THIS is the part I seldom see addressed, though I see a lot of ready-made excuses bandied about that will NEVER be of value in a real life situation. How can we miss this when it's so obvious???

[cainttype]

The OP is curious about the validity of a particular formula to guage a projectile's potential to "stop" a target, not the psycological preparedness of combatants. Whether discussing self-defense or hunting purposes, many basic principles overlap.
The links previously provided in this thread, by johniv and myself, address exactly what the OP is questioning. They also debunk the poor excuse for research foisted on the firesarms community by gun rags that was authored by Marshall and Sanow... Anyone interested in ACTUAL scientific research on the subject, by real professionals in the forensic field, owe themselve's a little time to devote to reading the data provided.
There are much better sources for information than a totally discredited book... Why the M/S book is still being quoted defies reason, especially from a group that professes too want to know facts and truths.

[rintinglen]

For what it's worth, in the 3 instances wherein 45 ACP was used that I have good knowledge of, two were hardball, and the 3rd was a 200 grain JHP of unknown or unstated manufacture.
The Marshall and Sanow Data is extremely suspect. I will not reference it.

[sqlbullet]

This debate is really as old as guns themselves. And every side of the debate has their own "formula" that they are certain tells the story.

Here is my take. The formula is the simple.

First, eliminate all the guns with which you can't shoot an el presidente drill in 10 seconds, under stress. For many (most?) there won't be any guns left at this point. So, get to the range until you have some guns with which you can shoot an el presidente in 10 seconds.

Next, get rid of all the guns you aren't willing to have with you anytime you are awake. No ones gun in the safe stopped an assailant.

For most people this is it. If you can run an el presidente in 10 seconds with a 380, or a 32, or even a 22lr, you probably are as well prepared as anyone.

Me...to be honest I need to get to the range.

All that said, I summarily dismiss any formula that doesn't account for velocity, diameter and mass. All three play a role. The Taylor KO factor does this. I don't know I really think it is the be all, end all, but it at least accounts for all the variables of the cartridge.

Next would be an evaluation of terminal ballistics, and there are too many variables there to reasonably account.

[9.3X62AL]

I've been at this "defensive shooting" study question for quite a while. It interested me prior to joining law enforcement in 1977, that interest increased markedly as a patrol deputy and expanded into firearms instruction in 1983......I remained an instructor until retirement in 2005. Long assignment as a case detective from 1993-2005 provided ample opportunity to assess and analyze gunshot wound dynamics from different perspectives. I also have the experience of receiving an on-duty gunshot wound in 1981.

I don't think any of these formulae do a very good job of predicting gunshot wound outcomes. The variables are far too many and far too over-lapping. All of these equations use one or more of the ballistic values--bullet weight, mass, velocity, or diameter--as a "squared" element to arrive at their conclusions. (I should note at this point that Hatcher's Index of Relative Stopping Power squares the element (frontal area) that actually squares itself in real life, but I digress). These formulae may have limited value in comparing calibers among one another, or bullets among one another--but in my experience they sorta fall on their derrieres when comparing outcomes to predictions.

It might be as simple as the thoughts given by mountain men to their armament during the fur trade era--that the bigger/nastier/meaner the critter or adversary, the bigger/heavier/faster your projectile ought to be. The end point becomes recoil management and aiming ability. Over-thinking these things is the province of admin pogues who DON'T get shot at for a living. I was blessed to work at an agency that offered a wide array of caliber choices and make/model selections that deputies chose for themselves and were quite willing to purchase on their own nickel. This has worked well for 38 years--it has a few disadvantages, but none of these have bitten us very hard to date.

[olafhardt]

I am just an old guy, not a retired cop, military or any kind of instructor. I know that no critter is likely to be as healthy after being shot as before.

[Potsy]

I've got diddley-doo experience on this one. But I've read on it for 25 years and have several relatives in law enforcement, so I thought I'd chime in with my didn't even stay-in-a-holiday-inn-last-night opinion.

As far as personal carry and home defense, the critical factor always seems to be having a gun (of any caliber) and being able to simply pull the trigger in a stressful situation (as mentioned before, don't take for granted that the simplest task is easy at that point). All other factors seem to come in a distant second.

As far as tools go, the best news seems to be that jacketed hollow points have improved tremendously in terms of reliable penetration and expansion in the last 25 years (and can still be sketchy at times).

In terms of caliber, I'd suspect that all (9mm, .40, .357 Mag & Sig, .45ACP) loaded with good JHP's, the statistical difference in performance would be pretty trifling.

Gun selection for personal concealed carry usually consists of a difficult-to-operate-for-the-person-who-shoots-once-a-year small frame auto.

Gun and caliber selection for law enforcement departments is usually dictated by high fashion, political correctness, Hollywood, performance "tales" (validated and otherwise) and price. Real world performance coming in waaay down on the list.

As far as any kind of "power index", I think the aforementioned TKO is the easiest to relate to. The only problem is (like all other formulae), it works great, right up till the bullet hits the hide.

[GREENCOUNTYPETE]

i have never shot a person but I have shot a hole lot of deer , and I can tell you after over 20 years of shooting deer with the same gun and brand of slugs it is all about where you hit them and their will to live.

no deer has ever gone anywhere with a severed spine that gravity did not take them

it takes time to bleed out even a severed artery leaving a 3 foot wide super highway of a blood trail in the snow takes near a minute to reach pile up

deer need neither a heart nor lungs to run and run fast for about 20 seconds

deer frequently go 100 to 200 yards with a 3/4 inch or larger hole through both lungs

the blood trail often slows to a trickle 50-60 yards before they pile up

you can shoot 2 deer of similar size in the heart lung area and one falls over and takes a minute or 3 to expire and the other runs a hundred yards

a half ounce of lead .62 inches across does not change any of these things significantly enough to tell the difference nor does a 50 cal conical , or 30 caliber bullet

and not necessarily from my shots a gut shot deer will go for hours before it finally expires

it isn't that uncommon to find an old arrow wound or previous years gun shot wound in a deer while your cleaning it or a good size hole gored by an antler that healed over

and from a cousin who used to hang out with some poachers who have since been relived of their hunting privileges by the state of Wisconsin and fined , a favorite tool of the poacher is a 22lr at the base of the ear they are only 10-20 yards away when they make that shot in the dark the light freezes them

if an ounce of lead .72 inches across doesn't do it on a 150-250 pound animal I wouldn't expect a pistol to do it

making it less about what your shooting and more about where your hitting

so shoot what you can shoot well , accurate and fast it is more about where you hit and what you hit than the difference in energy between rounds

[cainttype]

http://www.nasams.org/forensics/for_lib/Documents/1116600152.45/wound.htm

For anyone interested in professional research and conclusions...
The links provided there to book reviews should be of interest to the OP's intent.
I was told that the links provided to Firearms Tactical were down, so I'm providing an alternative link.

[Good Cheer]

There are no absolutes on stopping power. My family's insurance agent when I was a kid...was stitched diagonally multiple times from his left knee to his right shoulder with a MG-42. He still took out the machine gun that shot him....he lost his leg at the knee, all sorts of internal damage and won a Silver Star in the process. He was not a large man, maybe 5'7" and 140-150 lbs. He wasn't on drugs, and he was scared sh!tless....but multiple hits with a 8x57 Mauser couldn't stop him before he put a grenade into the nest.

Bad mistake. They shouldn't have made him mad.

[Good Cheer]

My take on the indexes and factors is that displacement (cubic inches per second) with adequate penetration are what matter.
How could you get any better one handed knock down than heavy wadcutters in a double action 45 Colt?
Oh OK, with heavy hollow point wadcutters!

[ofitg]

Since nobody else has mentioned it, an IWBA member (and engineer) named Duncan MacPherson published a book titled "Bullet Penetration". It provides models to predict ballistic gelatin penetration by non-deforming projectiles. It includes some heavy-duty math, but thankfully, MacPherson also presented the models in "graph" form for those of us who haven't been in a classroom in 30 or 40 years.

It may be the closest thing I've found to a "formula approach". If the penetration depth and projectile diameter are known, the wound channel volume (ie, "cubic inches") can be calculated.

[cainttype]

Since nobody else has mentioned it, an IWBA member (and engineer) named Duncan MacPherson published a book titled "Bullet Penetration". It provides models to predict ballistic gelatin penetration by non-deforming projectiles. It includes some heavy-duty math, but thankfully, MacPherson also presented the models in "graph" form for those of us who haven't been in a classroom in 30 or 40 years.

It may be the closest thing I've found to a "formula approach". If the penetration depth and projectile diameter are known, the wound channel volume (ie, "cubic inches") can be calculated.


MacPherson's "Bullet Penetration - Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma" is prominently featured and profiled in the recommended reading list contained in the links previously provided.
The Firearms Tactical link is currently down. Hopefully it will return to operational status soon. There is enough quality info contained there, and in it's referenced links and books, to keep anyone interested busy reading for quite some time.

[olafhardt]

Since nobody else has mentioned it, an IWBA member (and engineer) named Duncan MacPherson published a book titled "Bullet Penetration". It provides models to predict ballistic gelatin penetration by non-deforming projectiles. It includes some heavy-duty math, but thankfully, MacPherson also presented the models in "graph" form for those of us who haven't been in a classroom in 30 or 40 years.

It may be the closest thing I've found to a "formula approach". If the penetration depth and projectile diameter are known, the wound channel volume (ie, "cubic inches") can be calculated.
In dressing ģame shot with nonexpanding projectiles I have seen wounds with a much larger.cross section than the projectile.