Dear They1,
thank you for your replies....it could be interesting for you that I live in a country not very far from Bassano del Grappa....in fact I live near the border between Italy and Slovenia....I am very happy that you like your trip in my country!
*I very much enjoyed my trip there. I've always been interested in cultures, history and architecture.
I found so much interesting while I was there, including the bridge that still had bullet holes from WWII. I also found time to take the one hour train ride down to Venice. A great time, and met many great folks. (The food was good too...
)
I will look forward to visiting again some day.
Such history and cultures need to be preserved.
I felt the same way when I was in Cartegena, Columbia (the old city). How cool!
I need to explain better my previous statement. In fact I wrote:
That's what I mean.
If I take two rounds from the same box, for example two 135 GD as in your example, and I fire them in the same revolver, for example a snub nose as in your example, a muzzle velocity variation of about 2 m/s between one bullet and the other is not unusual at all.
I suppose for semplicity that expansion will take place once the soft tissues completely filled the cavity after the air bubble full compression.
The bullet number one has a muzzle velocity of about 259 m/s and the bullet number two has a muzzle velocity of about 261 m/s. I suppose too that the target, be it a ballistic gel block or a bad guy's body, is near the revolver muzzle so that it's possible to assume that the muzzle velocities are similar to the impact velocities.
With rough calculations is possible to note that the compressed bubbles have about the same volume when fully compressed (..the compressed air bubble for bullet 2 is negligibly smaller..) and that the energy that the bullet spend to compress such bubbles is similar for the two cases (..negligibly higher for the faster bullet..).
The energy spent is about 3.5J while the KE of the two bullets before the compression is respectively about 293 and 298J.
If the energy lost in the air bubble compression has such a marked influence on bullet expansion of bullet one(..the slower that flies at the same velocity as in your example..) I would expect that a normal variation of about 2 m/s in the impact velocity overcomes the problem of such energy lost because the KE available for the second bullet after the bubble compression(298-3.5=284.5) is a bit higher than that of the first bullet when it doesn't have to compress any air bubble in its nose (293).
The data of the manufacturer(CCI Speer) for the 135 GD shows this bullet launched at 860 fps has about 842 fps at 20 yards of distance from the muzzle.
It means to me that if the energy lost in the air bubble compression has such marked effects on the bullet expansion I would expect too a great difference in terms of bullet expansion/penetration behaviour when the soft target is near the muzzle or when the same soft target is at a distance of about 8 yards or more or even using two revolvers of the same type with the same barrel lenght and manufactured by the same company when there are very slight differences in barrel bores and cylinder to barrel gaps as it's usual.
The rough calculations of the time it needs for the tissue to fully compress the air bubble or for the tissue to fill the empty cavity in the nose shows that such time is very similar (..negligibly less with the bubble compression...the bullet is a bit slowed by this compression but the tissue needs to travel a bit less to fill the cavity because the space occupied by the compressed air bubble) with a stagnation pressure difference of about 1.5% with a bullet velocity of 850 fps (259 m/s).
*Your base assumptions are correct. And while one can establish "hard-line" numbers to explain a given criteria for scientific proof of theory, perhaps, rather than banging formula to the extent that it makes our heads hurt, I could provide an analogy that would explain the broad-spectrum of HC interaction performance;
Two vehicled are traveling towards each other at 50mph (80kph for you 
).
Vehicle #1 has an Airbag, Vehicle #2 does not.
Driver of V#2 is fatally injured, while driver in V1 walks away with scratches a bruises. Why?
...I need to add that's it's not a critic to your interesting work....only some thoughts that comes in my mind about the topic....I haven't any reason or will to criticize anyone....I am here only to learn more about wound ballistic much like a student....
*Noted...appreciated.
Please note that i am not an expert on wound channel ballistics. there are many who are far more qualified on that subject than I am. Many on this very forum.
...just to end this long (...maybe too long...I'm sorry..) post....
*Never aplogize for making sense.
Your questions are well thought-out, and you reserve conlusions until you gather facts. Bella.
"A wise man speaks because he has something to say; a fool because he has to say something". -PLATO
there is an old trick to promote a rapid and quite reliable expansion of bullets with a cavity in the nose....I guess that if the nose is full of liquid you don't need to wait for the nose cavity to be filled by the soft tissues and after that it's already full of a real liquid and not will be full of a fluid-like material like the soft tissues...the problem to solve is to find a way to lock the liquid in place...or to use some material that is solid at room temperature and liquid when the bullet heats on firing.
*That's been bantered about for eons; personally, I see too many issues with that concept, too many to discuss here in true detail, but just a few:
1. While the "concept" of a liquid-filled cavity would in-fact eliminate the need to eliminate air, how would you reliably contain that liquid?
Even in it's static state, the liquid will ALWAYS want to escape. A wax cap for example, would be suceptable to heat, handling, storage, etc.
An Epoxy-class cover would increase resistance on contact with a target.
Any metal or other alloys would pose exhaustive issues in manufacture.
2. Any liquid would no-doubt increase buller overall weight, and any attempt to compensate for same would likely decrease bullet-wall strength.
3. It would be highly unlikely that any cavity filled medium could, or would react to transform from a solid to liquid state based on heating. Consider the actual time involved, and the time it would take from the firing sequense, to transfer its heat through the bullet, to the medium and liquid-change state.
4. A manufacturer would ALWAYS have to insure a completly air-free cavity everytime. Otherwise bullet instability in-flight would almost be inevitable.
5. Bullet walls would likely have to be much thicker, considering the liquid would exponentially react to the rapid acceleration, and try to reshape itself accordinlgy (equal and opposite reaction, fluid dynamics, as it were)
All the best
Andrea
P.S.: on yesterday I had an odd idea .... I thought about a test with a pistol inside a vacuum chamber .... but apart highly probabilities of non negligible muzzle velocity variation of the bullet compared to the same fired in air.... I guessed that my colleagues were not very happy because the pollution by the firing residue and ballistic gel(..what's its behaviour in vacuum?..) on components, gauges and pumps
Originally Posted by MK108
Reply With Quote
Bookmarks