Performance summary of .380ACP JHPs in ballistic gelatin


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Brass Fetcher
June 20, 2010, 10:12 PM
This is a revised version of the .380ACP JHP results that I posted a few months ago. The difference is that I established a framework to measure ammunition terminal performance and ran the ammunition results through this process.

The different cartridges are given points for, and ranked according to :

- Did the bullet penetrate at least 8.0 on average, in 10% ballistic gelatin? (30 points maximum)
- Did the bullet penetrate between 10 and 12.0 on average? (10 points maximum)
- Cutting perimeter of the bullet (6 - 30 points, depending on actual perimeter)
- Were bullet fragments thrown outside of the track cut by the bullet? (0 or 10 points)
- Do the cartridges have case mouth and primer waterproofing? (0 or 10 points)
- What was the lowest velocity at which the bullet expands?

The points are added up and the bullets are ranked on a scale of 100 points. Primary goal here is to address the overall suitability of an ammo type for usage in concealed carry applications.

Please let me know what you think!

Thank you,
John

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CaptainHook
June 20, 2010, 10:24 PM
Great write up, thanks! Was interesting to read after looking at a Taurus TCP this afternoon.

duns
June 21, 2010, 12:15 AM
General comments

The fundamental problem with any scoring system is that it is based on a subjective model of what is important. What does the final score correlate with in real life? If it correlated with one-hot stopping probability for a torso shot, that would be really useful. However, I think scores such as this don't correlate with anything that matters in the real world. Indeed, there is not the data to develop a real world correlation.

There is a danger if your system catches on that that cartridges will be designed to obtain a good score and this could inhibit future progress in cartridge development. We really don't have a good understanding at the moment of how different parameters interact.

When considering any one parameter (you have 6 parameters), it is relatively easy to score the cartridges on an individual parameter. But it is not easy to combine these scores in a meaningful way. In effect, you have a weighting system in operation on the different parameters and that weighting system is highly subjective. I know you don't apply weights as such but when you assign different point ranges to different parameters you are effectively using a system of weighting factors. If you had a different set of implicit weighting factors, you would obtain different orderings of the effectiveness of different cartridges. This is the fundamental problem.

According to Marshall and Sanow, earlier systems for ranking cartridges include:


Julian Hatcher Relative Stopping Power (circa 1900)
US Justice Dept. Relative Incapacitation Index (1970s)
Dallas Area Southwest Institute of Forensic Sciences Test Protocol (date not given)
FBI Wound Value (1980s)
Border Patrol Test Protocol (1990s)

Marshall and Sanow appear to say that the Justice Dept. methodology matched best with street shooting data. It would be useful if your paper would discuss the earlier methods and demonstrate how your methodology improves on them.

Specific comments



Your minimum sample size is 3. I would suggest on a sample size of 3, the results will not be very accurate. How repeatable are your scores? If you do the tests several times over with a sample of 3, would you get different rankings of cartridges for each repeat? I suspect you might.
One of your parameters is the minimum velocity for "expansion". You define expansion as any part of the recovered bullet being wider than the original diameter. This would be better described as minimum velocity for "onset of expansion".
Your scoring system suggests that you consider a penetration depth of 10"-12" to be optimum. But if I understand your system correctly, you give 30 points for a cartridge that results in more than 8" penetration and 10 extra points if penetration is in the range 10"-12". So a bullet that achieved 24" penetration would still get 30 points (24">8")? Should you start subtracting points as penetration goes above 12"?
You could eliminate waterproofing as a factor by simply requiring that any SD round should have it. Not so much for water seeping in due to rain (I suspect that's not going to happen in practice) but for condensation in storage.This would reduce the number of parameters from 6 to 5.
You give extra points for fragmentation. Fragmentation is a tricky issue. Too much fragmentation early on could result in most of the energy being expended in shallow wounding.
Your model does not distinguish between early and late expansion. You give a lot of points for both expansion and penetration. To get a good score, a manufacturer could design a bullet that expands very late in order to get a high score on both these parameters. A bullet that expands early and so gets less penetration could get a lower score but might be as good or better because it gets larger wound volume.


Conclusions

I think your paper is a great first draft (thanks for putting so much work into it) but I think it needs more development, and justification, is to gain any widespread acceptance.

jbkebert
June 21, 2010, 12:19 AM
Great info thanks. It's funny that people go on and on about the cor-bon ammo. In a side by side comparison it ranks poorly.

Brass Fetcher
June 21, 2010, 07:50 AM
@Duns - Thank you for the feedback. You make some very good points ... (I'll get back to your post more this evening when I have more time )

Item 1. costs a lot of money and takes a lot of time to do more shots. My preference here is to keep updating the same document, and keep the date clearly visible on the first page. That way, people can see that more shots have been added to increase the sample size.

2. Good point. The term will be updated.

3. I like the idea for subtracting points for rounds that go over 12". My emphasis is on placing greater weighting on rounds that do more damage most of the time, than going for very deep penetration and minimal damage to the shallow tissues.

4. The waterproofing factor is likely going to remain on there - its not a critical factor (although I think that all rounds -should- have it) to terminal performance, but it paints an overall picture of suitability for CCW.

6. I've never seen a JHP go deeper than .75" in gelatin before the damage indicated that the round expanded fully... While I guess its possible for a manufacturer to work the FEA on a bullet to try to get it to take longer to deform, it seems like there isn't a whole lot of 'delay' that can be built into the bullet.

Give me a couple of days to look over these changes.

Thank you for the in-depth feedback.

John

usp9
June 21, 2010, 09:01 AM
Another very useful, informative report by JE223. Thanks for the time, expense and efforts expended. This is a real asset for all of us mousegun users.

CDW4ME
June 21, 2010, 09:03 AM
Even if people don't agree with the rating scale, this was interesting.
I've chronographed my P3AT and obtained nearly identical velocities for the Federal Hydra Shok and Remington Golden Saber as what you reported.
It's good to see the bullets do expand in gellatin at those velocities and still provide adequate penetration.

bratch
June 21, 2010, 10:32 AM
Thanks for the work. It is very interesting and relavent with .380 popularity these days.

Some input:

You identified the Speer Gold Dot as a Speer XTP in the Speer table at the end.

Why were some rounds recorded against summer clothing, winter clothing, or bare gel? In my opinion it would be an easier comparison if all bullets were shot into the same media and covering instead of trying to compare Gold Dots into bare gelatin and Hydra-Shoks in summer clothing.

Once again thanks for the work its great.

bannockburn
June 21, 2010, 08:11 PM
JE223

Thanks for the research and testing. While I too question your use of different media (gelatin, summer and winter clothing), in a sort of apples to oranges comparison, I found your results quite interesting. Keep of the good work.

searcher451
June 21, 2010, 08:15 PM
+1 on the many positive comments regarding the fine write-up and report, JE223. It was certainly interesting reading, especially considering the fact that I still carry a Walther PPK/S from time to time during the summer months.

Brass Fetcher
June 21, 2010, 09:56 PM
Good point about the mixing in the heavy clothing with the bare shots. Unless someone is paying attention to that detail, they may get a wrong impression of the rounds effectiveness.

>The fundamental problem with any scoring system is that it is based on a >subjective model of what is important. What does the final score correlate >with in real life? If it correlated with one-hot stopping probability for a torso >shot, that would be really useful. However, I think scores such as this don't >correlate with anything that matters in the real world. Indeed, there is not >the data to develop a real world correlation.

Good point. But I think that it is important also to remember that there is no such thing as a one-shot stop against a fully-motivated attacker, unless their central nervous system is incapacitated.

What I'm looking to do is to express the general utility of a given cartridge, as will be explained below.

>There is a danger if your system catches on that that cartridges will be >designed to obtain a good score and this could inhibit future progress in >cartridge development. We really don't have a good understanding at the >moment of how different parameters interact.

I don't see a problem with manufacturers trying to tune their bullets to get a higher score, as long as the metrics reflect positive wounding characteristics.

>When considering any one parameter (you have 6 parameters), it is >relatively easy to score the cartridges on an individual parameter. But it is >not easy to combine these scores in a meaningful way. In effect, you have >a weighting system in operation on the different parameters and that >weighting system is highly subjective. I know you don't apply weights as >such but when you assign different point ranges to different parameters >you are effectively using a system of weighting factors. If you had a >different set of implicit weighting factors, you would obtain different >orderings of the effectiveness of different cartridges. This is the >fundamental problem.

This is essentially the same system that the FBI uses, I just have it geared more realistically towards civilian CCW.

>According to Marshall and Sanow, earlier systems for ranking cartridges >include:

> * Julian Hatcher Relative Stopping Power (circa 1900)
> * US Justice Dept. Relative Incapacitation Index (1970s)
> * Dallas Area Southwest Institute of Forensic Sciences Test Protocol (date not given)
> * FBI Wound Value (1980s)
> * Border Patrol Test Protocol (1990s)

>Marshall and Sanow appear to say that the Justice Dept. methodology >matched best with street shooting data. It would be useful if your paper >would discuss the earlier methods and demonstrate how your methodology >improves on them.

That's not surprising since Marshall and Sanow seemed to be fixated on kinetic energy transfer. RII measured the diameter of the temporary cavity obtained in ballistic gelatin - a rough expression of how much kinetic energy was transferred to the medium at that depth. This is accounted for in the weighting factor that gives 30% credit to bullets that penetrate at least 8" but less than 10".

My preference would be to hit the target as hard as possible - a person can still survive for 15 seconds after being hit in the heart, for instance. If a bullet stops an inch short of their heart, they are still likely to be very injured. It's a matter of playing the percentages and realizing that the heart and spine is a very small target, that we are not guaranteed to be able to hit on every shot. RII was very good in that it give large credit to doing lots of damage early in the penetration track - but this is not the whole picture.

>Specific comments

> 1. Your minimum sample size is 3. I would suggest on a sample size of 3, >the results will not be very accurate. How repeatable are your scores? If >you do the tests several times over with a sample of 3, would you get >different rankings of cartridges for each repeat? I suspect you might.

Most definitely. The system is designed to be expandable.

> 2. One of your parameters is the minimum velocity for "expansion". You >define expansion as any part of the recovered bullet being wider than the >original diameter. This would be better described as minimum velocity for >"onset of expansion".

Good point.

> 3. Your scoring system suggests that you consider a penetration depth >of 10"-12" to be optimum. But if I understand your system correctly, you >give 30 points for a cartridge that results in more than 8" penetration and >10 extra points if penetration is in the range 10"-12". So a bullet that >achieved 24" penetration would still get 30 points (24">8")? Should you >start subtracting points as penetration goes above 12"?

Most definitely. I will build in a method to subtract points for bullets penetrating over 12.0".

> 4. You could eliminate waterproofing as a factor by simply requiring that >any SD round should have it. Not so much for water seeping in due to rain >(I suspect that's not going to happen in practice) but for condensation in >storage.This would reduce the number of parameters from 6 to 5.

True indeed, moisture seeping in through time is more of an issue. As simple as it is to put sealant on a casemouth, it should be done in order to increase the reliability of the self-defense firearm.

> 5. You give extra points for fragmentation. Fragmentation is a tricky issue. >Too much fragmentation early on could result in most of the energy being >expended in shallow wounding.

I would argue that too much attention is giving to the idea that the first shot fired is going to hit the target with the perfect penetration path and that will be the end of the fight. For instance, a fragmenting round hitting the bicep of an attacker may tear the muscle an additional amount, which may be sufficient in disabling their entire arm. Being down one arm may take more fight out of them then a non-vital wound to the chest.

> 6. Your model does not distinguish between early and late expansion. You >give a lot of points for both expansion and penetration. To get a good >score, a manufacturer could design a bullet that expands very late in order >to get a high score on both these parameters. A bullet that expands early >and so gets less penetration could get a lower score but might be as good >or better because it gets larger wound volume.

All JHPs expand within 2 bullet diameters of penetration depth (IE 9mm expands fully within 18mm or about 0.7" and so on)

>Conclusions

>I think your paper is a great first draft (thanks for putting so much work >into it) but I think it needs more development, and justification, is to gain >any widespread acceptance.

Thank you for that. The thing that I would like everyone to remember is that this is a growing system ... the big deal here is to develop a way for the ammunition consumer to make more informed choices about what they load for self-defense.

Thank you,
John

LightningMan
June 21, 2010, 10:25 PM
I found your research testing interesting, I would also like to see other bullets/ammo tested like Buffalo bore & critical defence. Again very nice, thanks. LM

benzy2
June 22, 2010, 12:38 AM
I truly appreciate the effort that has been taken to both test and report the results. I think the data is very useful for the many people who decide to carry .380. The only thing I personally disagree with would be that anything over 12" is a hindrance. I know we are down to opinion as to what the idea performance numbers would be, but I would think somewhere in the 14-18" range to be absolutely ideal if poor angles are to be taken into account. I do agree that there is a point where too much penetration is bad, both in energy dump and in potential down range damage. I'm just not sure 12" is the cut off. There are many 300lb+ people in the local area, and while I don't see many of them being a threat, I know 12" of penetration isn't going to reach the spine in some of these people. It will punch a clean hole through most, but at least locally, it is going to be ineffective on a large enough percentage of the population to be at least a concern. My point being that if you subtract for performance deeper than 12" you will have made it so a bullet that penetrates 12.1" will score less effective than one that penetrates 8" and personally that seems a bit skewed. I know it's tough to create the "perfect system" but I would caution how much you penalize a bullet the just barely goes too far rather than one that may not go far enough.

Brass Fetcher
June 22, 2010, 08:33 PM
Benzy, thank you for the feedback. I envision it being something like -1 point for every 0.5" over 12". That way, the benefit of having a bullet that can go 10-12" will be negated if the round goes to 17" or beyond. The numbers in this area need to be reviewed, but that is something that makes sense to me.

I look at defensive shooting events exactly as one would look at any other type of fight (say, boxing or MMA). It's usually a contest that involves multiple strikes being traded by opponents, both people are fully motivated to stay in the fight (because of the prize money, pride, etc). Very rarely do you see one of the opponents get knocked down with the initial punch or kick.

If we are only 'swinging for the fence', IE planning that our shooting will be accurate enough to hit the opponents central nervous system (AND put them out of the fight), I think we miss a lot of the benefits of ammunition that would take more fight out of the opponent with a hit anywhere on the body.

Most criminals will probably give up after being shot - the ones that continue to fight, will need to be physically stopped. If you shoot them in the heart, they will still be able to fight to their physical capability for 10-15 seconds. Cut their bicep and shatter one of their arms with a 'poorly placed shot' and you have incapacitated them in a few microseconds. If their arm cannot physically aim their weapon or stab, etc, they will either have to adapt by changing arms or giving up.

Same with a disabling hit to the leg - nearly instant incapacitation in that they will be unable to run after you to stab, or to run for cover. Yes, they are still able to fight, but they are basically unable to move or adapt to the threat that you now pose to them.

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