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
