Hollow point ammo... And why heavier are more consistent

[marine6680]

Been thinking on this... It seems to spark a lot of argument online.

First, know that I am writing this on free periods at work... On a phone. Spelling and punctuation may be off, and it may be a little disjointed from stopping and starting. Should be fine overall though.


Two sides... Those who think light and fast are tops, and those who think a little slower but heavy win the day.

Most everyone is in agreement that good penetration is important. Some argue that a large wound cavity is just as or more.

The light and fast crowd will point to the massive damage cavity left in the test medium of fragmenting types, and say that the non-fragmenting rounds can penitrate ten inches usually and sometimes twelve or more, while still having a large cavity. That massive wound cavity is great, and speeds bleeding and helps spread damage to organs even if the shot isn't the best.

The heavy crowd point to those tests and say that "sometimes" is not good enough, when final penitration can vary so greatly from as little as six inches at times. And 10-12 inches is still less than ideal. They say that the heavy round reaches 13-15 inches with every test in ballistics medium, and that the wound cavity created is more than sufficient to increase bleeding over a simple clean hole.

A lot of enphasis is placed on "energy" or "stopping power"... This seems silly to me. It is only one measure that is important when determining a bullets potential.

I doubt this argument will ever be settled...



What I think can be explained is why heavy bullets are more consistent.

When looking at a projectile you have 3 important factors.

Kinetic Energy
Momentum
Inertia

Everyone knows energy... It's touted everywhere.
E=.5(m*v^2)
Velocity squared... A change in velocity makes more impact on energy than a change in mass. It's why people chase velocity... And it is what those that like light and fast, point to as validation.

That's all well and good, but what of the other two measures, momentum and inertia?

In a pistol round, I think they matter more. Why?

Energy of pistol rounds is fairly low, so even a full transfer of it does little work overall.

Momentum is the property of objects in motion.

Inertia is an objects inherent resistance to a change in its current state from external stimulus. Be it sitting still or moving, it wants to stay that way, unless acted upon externally.

Momentum =m*v
You see that here velocity does not have an advantage of being squared.

Inertia is related to the objects mass

Mass is in all three measures but velocity only two.


So let's think about what happens to a projectile as it enters a test medium... Let's assume a non-fragmenting type.


As soon as the projectile first contacts the medium, it begins to loose velocity, mass will more or less stay the same.

Looking at the equation for energy shows that it will be loosing energy fast, as velocity slows. Remember, changes in velocity affect the energy levels more than mass.

Momentum... It looses momentum as velocity decreases, but at a slower rate.

Inertia... It stays the same. The projectile's velocity does not affect it's inertia.


That to me seems to point to the fact that starting with a heavier mass is better.

Long range shooters know this... They can't prevent velocity loss, but performance down range can be conserved longer.

Yes... Different needs and circumstances... But the desire to retain energy/momentum over a given distance is the same.

In defensive use, we want to retain energy/momentum over the desired depth of penetration. A nominal 15 inches according to most experts.


Whether the fast and light crowd are right about energy transfer and wound cavity being more important or equal to overall penitration... Or the the heavy and slower crowd are right... We may argue that forever.


I hope I was able to at least show why heavier rounds perform more consistently with regards to penitration... Which is the only quantifiable performance figure we can really look at. Energy transfer and effects of wound cavities are harder to test and predict results, due to testing being limited to gel and not living entities.


Me I am in between the two sides, with a leaning to heavy. Feeling that accurate shots and proper penetration is the best bet. Though I am open to a lighter round that fragments but still retains a core that can penitrate to proper depths. Moch testing would need be done though to show it performs well.

[Nanuk]

My experience is that low weight low energy rounds are less consistent, say like a 380 ACP. I like big and fast if using that analogy, I really like the 357 magnum is that big or small? What is your definition of big? Small? Slow? Fast?

[marine6680]

Example... 9mm

Light weight = 115gr and less

heavy = 124gr and up

[481]

That to me seems to point to the fact that starting with a heavier mass is better.

It is. A bullet's motion is governed by Newtons Second and Third Laws of Motion, F=ma and mv = mv. Both equations show that force and momentum are directly related to mass so having more mass means that having the heaviest possible bullet is desirable.

[iraiam]

I am a firm believer in heavier for caliber bullets. Some people look at velocity and are impressed, as a former physics student; I am not impressed by velocity by itself.

For example; I saw a box of 9mm ammunition that was marketed as self defense ammo, a 50 grain bullet at 2000 fps. At that high velocity; calculated muzzle energy will be notably higher, but it will shed energy much faster than a heavier projectile, which would lead relentlessly to less penetration. Up close and personal, I'm sure this ammo would be devastating to a t-shirt clad home invader, but IMO there are too many variables in circumstances to put much faith in ammo like this as a general carry ammo.

[Sport45]

I pick the profile that works best in my guns and the weight that matches point of aim best with my fixed sights.

Revolvers get 158gr LSWCHP in .38spl, and 125gr JHP in .357mag. Haven't tried anything else in decades...

That is 'good enough' for me and I'm not going to spend the money it takes to test new loads in my guns. YMMV

[marine6680]

Revolvers require much less testing than a semi auto.


The only light bullet I have seen that looks promising is the DRTs. It fragments about 2-3 inches in, but retains a central core that penetrates. It's still not perfect though, final penetration is only around ten inches.

Lower recoil in small light autos is a benefit though.


My preferred 9mm load is 124gr HST from Federal.

[Bezoar]

i dont know, the colt saa in 45 colt was designed to penetrate a horse at 70 yards.

ive seen alot of late 90s dash cam video showoing people shot at 10 feet with 9mm "police only ammo' taking 5 hits before they stop walking towards the shooting officer.

[Mobuck]

If you're not going to push a HP fast enough to expand, you might as well be using a flat nose FMJ. I shoot 124 grain GoldDots because I know they'll expand and penetrate far enough to cause serious wounds. I've tested 9mm 147 grain GoldDots and they don't offer what I'm looking for(from a pistol).

[Deja vu]

I tend to be a middle of the road guy. I like the medium weight bullets.

for 9mm I think 124 would be the medium. 115 is the light and 147 is the heavy. For 357 Magnum I like the 158 grain. 110 and 125 are the light end and 180 and 200 are the heavy end.

The same with rifles. I shoot alot of 45-70. For that light bullets are 250-300 Grain and Heavy are 405-500 grain. I like 350 grains but shoot a lot of all 3.

[KyJim]

If the shooter does his or her part in carefully selecting ammo, the debate between light vs. heavy is not nearly important as it used to be unless barrier penetration is important; e.g., auto windshields. This is due to better bullet construction. For example, here's a test where a 115 gr. standard pressure Gold Dot passed through four layers of denim and traveled 17.5 inches in test medium and expanded to approximately .52 inches. http://www.youtube.com/watch?v=v2s82NCLKQI.

Keep in mind that even the 115 gr. Winchester Silvertip which was criticized in the wake of the Miami Shootout, actually performed decently, striking the BG from the side and came to rest less than an inch from the heart. That bullet technology is 30 years old.

On the other hand, manufacturers also make rounds with medium or heavy bullets that expand well at lower velocities than old hollow point design. Get a Gold Dot 158 gr. . 38 special traveling over 800 fps and you'll get adequate expansion and penetration. For example, here it expanded to .544 and went just over 12 inches into the test medium after going through four layers of denim. http://www.youtube.com/watch?v=k890Rio2oBY

You have to do your homework, though. You simply can't go out there and buy just anything.

[FireForged]

hard projectiles punch holes in less substantial objects... thats about as deep as I get when talking about bullets. My primary consideration is functioning reliability not absolute ballistics.

[Oysterboy]

What should be taken in consideration is the rate of expansion of a hollow point. If expanded too early you fail to get the ideal penetration. If expanded too late you get a punch through. Also a failure to expand as well.

Kinda hard to design an ideal hollow point.

[loic]

Originally Posted by marine6680

Example... 9mm

Light weight = 115gr and less

heavy = 124gr and up

I shoot and reload what is more acurate for my pistol, and for it is the 124 gr (berry hollow base, plated bullet) to ME , accuracy is the most important, if the first shot doesnt stop my target, I still have 18rds left....

[zombietactics]

Generally these kinds of discussions get filled with a whole lot of stuff attempting to explain things in terms of physics and science ... while simultaneously demonstrating a grasp of the particulars which would get you and "F" on any physics exam.

Alternately (as in the case of Marshall/Sanow, Taylor, Hatcher, Ashby, etc.) they take an observed result and try to pigeon-hole a pet theory into "proving" it. If the answer is 4, you can make up an infinite number of equations to describe that result ... which explains why that approach is scientifically unsound. That doesn't stop people who desperately want to BELIEVE something.

I'm just going to shut up (this time) and note that a whole lot of nonsense gets cleared up with about 10 minutes of lab time.

Consistent, repeatable results ... controlling for all the known variables. Everything else is religion dressed up in drag.

[biohazard313]

.40 S&W 180 gr over 165 gr. stopping power over velocity. i prefer that the target drop in as few shots as possible. the heavier will be a bit slower but transfer more energy on impact. incapacitating the subject.

my $.02

[Nanuk]

I'm just going to shut up (this time) and note that a whole lot of nonsense gets cleared up with about 10 minutes of lab time.

Consistent, repeatable results ... controlling for all the known variables. Everything else is religion dressed up in drag.

Ahem, excuse me professor. But how do we know if our experiments in the lab translate into the real world?

Computer models and mathematical formulas only get you so far. The lab people like to dismiss anything that they cannot quantify in the lab. You are missing half the answer if you do it that way.

[ATPBULLETS]

On the other hand, manufacturers also make rounds with medium or heavy bullets that expand well at lower velocities than old hollow point design. Get a Gold Dot 158 gr. . 38 special traveling over 800 fps and you'll get adequate expansion and penetration. For example, here it expanded to .544 and went just over 12 inches into the test medium after going through four layers of denim. http://www.youtube.com/watch?v=k890Rio2oBY

Nice video....158gr at 850fps.....magic...

Thanks for the link KyJim

[zombietactics]

Originally Posted by Nanuck

... Ahem, excuse me professor. But how do we know if our experiments in the lab translate into the real world? ...

(with no disrespect to you personally)

It depends upon the nature of the experiment, what it proposes to demonstrate, and sometimes how well the experiment models (or serves as a useful analog) for a real world problem.

For instance when we use ballistic gel as a test medium, we know that it does not act exactly like any cross-section of a human being. It's really a rough analog for the viscosity and density of muscles tissue. It lacks all sorts of things ... fibrous muscle structures, membrane layers ... the list is pretty huge in that regard. It does one thing pretty well though ... serves as a consistent test medium for penetration and expansion performance, which extrapolates in meaningful ways to real-world performance. We observe different, complimentary but not contradictory results when comparing "the lab" to "the street".

Originally Posted by Nanuck

Computer models and mathematical formulas only get you so far.

I haven't said anything about computer models, so I don't feel any responsibility to respond to that comment.

When we are talking about "mathematical formulas" however, we aren't just discussing made-up nonsense without a real-world point of reference. All of Newtons laws (and associated math) describe the real world - accurately - in mathematical terms. The fact that they do so is why we can send satellites into orbit and men to the moon. That kind of math allows us to predict with amazing accuracy what will happen in the real world.

Originally Posted by Nanuck

The lab people like to dismiss anything that they cannot quantify in the lab. You are missing half the answer if you do it that way.

I think it's more the case that if there isn't an adequate way to test something under laboratory conditions ... that's just admitted. It's not like you can hide something like that.

If you don't have an adequate test, that's one thing. If you observe something "in the wild" which seems to be contradictory to established physical laws, it's usually the case that you haven't taken the right measurements or something else is going on.

But what's going on a lot of the time in discussions like these is people WANT a certain result, and they just make up whatever math they want (or misapply physical principles) in order to "prove" it. That's exactly what Julian Hatcher and John Taylor did, and it's a common criticism of Ed Ashby as well. The fact that you can easily demonstrate that their theories completely fall apart both in the lab, in the field ... and contradict any sound understanding of the physical principles involved ... that doesn't just go away because some fan doesn't understand the science.

Note that both Hatcher and Taylor overemphasized weight and/or momentum ... and start to see the pattern.

My general observation is that people fall in love with certain metrics (like momentum) because they are easily calculated. Add to that set of faulty notions regarding how penetration happens in elastic/plastic structures (as opposed to fluid structures, which behave differently) ... and all of a sudden you're all over the map, and not really doing anything but expressing a raw opinion supported by nothing but bad physics and bad science. The people who want to believe the same conclusions come along understanding even less of the physics and science ... but support all that nonsense as somehow being "proof" or "evidence" of what they wanted to believe all along.

I've stopped worrying about this, but I thought your comments called for a thoughtful, respectful response.

[Oysterboy]

I do understand one thing for sure, a light object will yield to resistance faster than a heavy object in comparison.

[marine6680]

So your here now zombie?


We have shown in the other thread... where I actually had time to flesh things out better than this thread... and also others.

That you are the one misinterpreting the math and laws of physics.

You said many things that just don't jive with the laws of motion...Your zero force statement was just... wrong...

You haven't posted in that thread in a while, more was added, you should go look at it. There are more experiment results as well.


I have talked to people on this face to face, all good minds with a firm grasp of these things... all agree that momentum is key to penetration.

You seem intelligent, this isn't a bash on you, just a statement that you are incorrect.


You bash looking at results and then trying to give reasons to why the result happened... you say that isn't how science works.


You realize that the laws of motion, gravity, evolution, and many others all got their start from this process, and were later refined with controlled testing.


As I explained in the other thread, energy determines the cavity left by the bullet that is larger than the bullet diameter. Higher energy gives a larger cavity

But momentum determines the penetration depth.

Go to the other thread to see the math and explanations.



Also... I can honestly say, I have never received an F on an exam.

[zombietactics]

Originally Posted by marine6680

... you are the one misinterpreting the math and laws of physics. ...

Possible, but I don't think that's been demonstrated. I sort of lost interest once Ed Ashby's report was mentioned, as that's when I knew that a serious discussion was probably impossible. I mean that without any intent to insult, BTW.

Originally Posted by marine6680

There are more experiment results as well.

I shouldn't have to explain what was pretty obviously wrong with the "potato and nail" experiment.

Originally Posted by marine6680

I have talked to people on this face to face, all good minds with a firm grasp of these things... all agree that momentum is key to penetration.

You seem intelligent, this isn't a bash on you, just a statement that you are incorrect.

I appreciate the spirit in which those comments are offered.

I'd offer in return that I would be wrong if we were talking about penetration through fluid structures (where drag is a very big deal) or the penetration of shafts (like nails, or arrows) which experience increases in drag during penetration ... or penetration into inelastic solids with near zero plastic ranges (like a potato, lol).

Perhaps my mistake is in assuming that we are talking about the penetration of projectiles (i.e. "pellets" or "missiles" as commonly referenced in ballistics literature) into elastic solids with a wide plastic range. In such structures (muscle as an example) drag is a fairly insignificant factor.

Originally Posted by marine6680

You bash looking at results and then trying to give reasons to why the result happened... you say that isn't how science works.

Well, that's either a partial misrepresentation on your part or a failure to communicate well on mine. The test of a good hypothesis is not whether it matches a small subset of observed phenomena, but rather whether it can predict the results.

That's the problem with the formulas offered by Hatcher and Taylor for instance ... they came up with mathematical models which seemed to describe the observed behavior, but failed when the variables went beyond a very narrow range of values. Bad math, horrible physics ... yet some people still insist they were/are correct. Its' somewhat indicative that they also consider(ed) momentum a big deal.

As a metric, momentum doesn't tell you much of a predicative nature, which is another clue.

Originally Posted by marine6680

You realize that the laws of motion, gravity ... got their start from this process, and were later refined with controlled testing.

I am purposefully leaving out "evolution and many others" because it invites a lot of off-topic discussion which is unnecessary. The laws of motion were actually derived almost from pure philosophy, and confirmed by testing. The proof of their validity is their ability to accurately predict almost any (non-relativistic) physical phenomena involving inertia, action/reaction, acceleration, etc.

This predicative quality is key to any valid scientific explanation, as it directly invokes the principle of universal physical principles.

This conversation is at a point where it holds little practical value. If people simply choose duty-rated ammo in a common duty caliber, the differences in terminal ballistic performance will be nearly insignificant. However poorly someone reasons out the cause of those differences ... not an argument which holds my interest. Nobody is likely to get killed because they misunderstand the physics of this problem.

I am content to get paid to to scientific measurement for a living and leave it at that. I don't need anything more than that, the physics themselves and the fact the stuff I do "works" (both in the lab and in practice) to be content, and it's not worth by getting snippy (or snippier, lol) over it.

[Brotherbadger]

I am not impressed by velocity by itself.

Bingo. Velocity is an important factor, but it is only half the equation for me. Finding the right balance between weight and velocity is key.

[marine6680]

I will say zombie... You are easier to discuss with than many on the internet.

I would say that I believe that at handgun velocities, test gel is a semi solid that reacts like a fluid on impact. So describing the math in relation to fluid dynamics and particle motion through said fluid is the way to go.

You mentioned a study and some people that were brought up and made you step back from the topic... In all honesty, this discussion was the first I had heard of them...

I tried reading the linked study, and didn't make it far. I am unsure when it was done, but the lack of SI units and the mixing of so many other unit types, it hurt my head a bit.

This has gotten into less practical and into the pure physics behind it all.

For me, it's just good fun, I win, I lose, I learn, I teach... I just enjoy talking about the underlying rules and laws of the universe. Heck I even dabble in philosophy and psychology too.


This has provided more entertainment and enjoyment than most TV for a while, so I found it far from pointless.

[zombietactics]

I will say zombie... You are easier to discuss with than many on the internet.

I try, lol.

... at handgun velocities, test gel is a semi solid that reacts like a fluid on impact. So describing the math in relation to fluid dynamics and particle motion through said fluid is the way to go.

Ballistic gel is actually a "colloid", and specifically fluid microscopically dispersed within a solid. The properties exhibited are those of an elastic solid with a fairly wide plastic range.

In a strictly fluid medium, drag is a very big deal, and therefore momentum is as well. In a elastic solid (like gel, skin, bone or muscle), shearing resistance is the thing you are concerned with, and drag has very little to do with the problem, unless the penetrating object accumulates drag (like a spike or the shaft of an arrow). Shearing resistance does NOT increase with velocity in this type of medium. It actually decreases in elastic mediums. That's why KE is the big deal for these kinds of problems.

This has provided more entertainment and enjoyment than most TV for a while, so I found it far from pointless.

If I can make a suggestion, noodle away on the "potato experiment" for awhile. If you happen upon the "grand aha" which demonstrates it to be a worthless example, you'll amuse yourself to no end ... discovery is fun.

You'll also find it interesting to note that the "Taylor Knockout Formula" is being actively defended by some in another thread: LINK ... nonsense dies hard when people want to believe something which makes them comfortable with their assumptions, preferences or prejudices.