Originally Posted by
MK108
Dear They1,
thank you very much for your kind replies,
I need only to add that when I wrote about the possible airflow choking I did not mean the one that can happen during the flight of the bullet in air but I refer to the one that can happen in the first moments of the tissues penetration by the bullet...
..please, let me clarify....
...from your explanations I guess that you want to limit the energy spent in the compression of the air in the cavity. Sorry for my possible misunderstanding but I guess that in your design the air trapped in the cavity needs to be pushed by the tissue when the latter enters in the cavity so that the air escapes from the nose cavity through the tiny radial channels...
*In effect, you are correct. That's exactly what I'm doing.
However, porting of the cavity is only "the means-to-an-end".
I'll explain; The ultimate goal is to minimize the effect of the trapped air in the HP cavity, which, as a "compressible" gas, acts simply put, a "shock absorber", or "cushion" at the time a bullet makes contact with a target. (The same effect as a suspension system works so well on a car, as opposed to the go-carts we rode as kids)
By allowing that gas to be vented in a direction other than forward, the compression factor is negated, while at the same time, the cavity space is more readily exchanged with the intended medium (target tissue), which is obviously necessary to begin the expansion process. To date, the only real bullet design to address this issue, and an effective one I might add, are rounds filled with the semi-sillicone-based materials. And while this is a notable advancement, one should note that by it's own design, it's still a medium that MUST COMPRESS to be effective. In short, it's still a "second-stage" in the expansion process. (1. Bullet contact, 2.Compression, 3.Exchange, 4.Pressurize, 5.Expand)
The HC round basically eliminates that second stage, thus promoting, or enhancing the third. This "cascade" effect also causes the target tissue to "slam home" with greater force, and as a result, a bullet expands with greater force. (i.e. like being hit with a broom, or being hit with a bat.)
...if so it happens in a very short time and to be displaced through such tiny channels the air flow must have a very high velocity....so that the air flow in reality can be really slowed because the channels appears as choked...with the final result that you could have the air compression with or without such channels unless they have proper size and design, imho.
*I must say your knowledge and grasp on this subject is very lucid and well thought out. I'm very impressed.
Indeed, correct again...Please note that this project is in it's infantcy, and I am only the inventor, not the end-developer.
My original concept, and prototype testing of this concept, was simply to prove the viability of the concept itself. The ultimate Licensee, through their own R&D will no doubt have to "calibrate" port size, port count and port diameter for optimum performance based on the multitude of calibers, cavity sizes, velocities, etc..
...much like a syringe with a very small outlet and full of air...on moving the piston slowly tha air flows outside without great problems....but if you try to move the piston very fast it seems to be locked as there isn't any hole in the sirynge bottom...
*Good analogy.
Let's expound: While your example is dead-on, you must put this example into perspective;
Hypothesize for a moment several syringes with the same diameter nozzle. Now input the same amount of pressure applied to the plunger. The resistance to those plungers will be directly porportional to the cavity of air being expended. Would the resistance be the same, under the aforementions conditions when comparing a 30cc, 10cc or 1cc syringe? Of course not.
Now put into perspective the actually quite small area of an HP cavity, now add a 1/32 diameter port, now make that times 3 ports, and you can see how ultimatly small the ports can be, while still allowing rapid gas exchange with minimal impact on the bullets original strength, opening and design specs.
I got a hard lesson in this many years ago when I invented a "robotic photographic tripod". It was designed to allow a user to control all adjustments to a tripod, using only two micro-switches that were attached (by velcro) just unter the camera shutter button.
I did this by adding pneumatic actuators at the legs, wheels (retractable), boom arm and camera mount head.
Powering this was a control box which housed a compressor, battery, regulators and switching relays.
Ultimatly, the greatest challenge was calibrating pistons that would apply enough force to lock and release all lock points, while keeping operating pressures and volumes at a minimum.
In the end, the "Android-1" prototype was a way cool, rocket-fast, 60lb, $60,000 dollar project that went to BOGEN tripods in Bassano Del Grappa in Italy.
(Beautiful city btw, hope go go back and visit again one day.)
It seems that experience has served me well in this context.
..it comes to my mind that another possibility is that you want a continuos flow of air from the nose cavity through the tiny channels during the air flight in order to haven't any air inside the nose on impact with the body tissues....but even in this case the air needs to be displaced continously through this small orifices...
*Not really. Ideally, I'd like there to be no reaction to a bullets' laminar airflow during flight, but that's not possible. The effect with the ported design is "negligable", but inevetable. There will be some air exchange, and with a "bullet-to-bullet" comparison, the HC round will have a slightly lower in-flight cavity pressure compared to a typical HP round, but I don't find any significant effect until the "metal meets the meat".
...about my comparison between the KE lost in the air compression as in your example and the KE variation for the bullets in the same box of ammunition in my example my guess is that if the energy lost in air compression is so an important factor in the expansion behaviour of a hollow point bullet maybe I am wrong but I can expect a wide variation of expansion/penetration behaviour even from bullets with conventional hollow points fired from cartridges taken from the same ammunition box all other things being equal.
*I must admit, I'm not quite sure what you're asking here...
Are you suggesting that conventional, identical HP rounds would have variable cavity pressures/dynamics?
All the best
Andrea
Senior Member
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