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Discussion Starter #1
So. I have been working on modifying factory .303 rounds to increase cavitation. Any ideas, suggestions and tips would be welcome. I think I am making headway but I have neither the time or money to really develope the idea. Doing what I can.
 

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Discussion Starter #3
Thanks a bundle.

I get what the publication is saying but has anyone done much research into follow-up cavitation. By that, I mean cavitation following the bullet. To simplify my questions I'll state that I have been furrowing a spiral pattern against the rifiling of my weapon and have noticed a significant increase in air disturbance behind the bullet. Am I chasing ghosts?


Again, thanks for the link.
 

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I get what the publication is saying but has anyone done much research into follow-up cavitation. By that, I mean cavitation following the bullet. To simplify my questions I'll state that I have been furrowing a spiral pattern against the rifiling of my weapon and have noticed a significant increase in air disturbance behind the bullet. Am I chasing ghosts?


Again, thanks for the link.
Cavitation doesn't occur in air.
 

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I have been furrowing a spiral pattern against the rifiling of my weapon and have noticed a significant increase in air disturbance behind the bullet.
What does this mean? How did you detect it?
 

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Discussion Starter #7
Cavitation. again

The range I use has light to moderate vegitation. When I fire a factory round at a target there is very little if any disturbance in the surrounding ruffage. When I fire my modified rounds at a target there is something between a 3 to 5 foot vacuum that whips the surrounding vegitation around. I haven't documented it yet since I was a bit nervous at the first test.
I will record my next test and provide a link. I am a fan of critisim. If you think I am wrong then flat out say it. I am ok with that. Otherwise. If you are near illinois we could get together and see if I am on to something.
 

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Discussion Starter #8
"Cavitation only occurs in liquids."
Wouldn't Cav start to take place before the object reached the subject?
The object is already displacing air in its flight path, right?
 

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"Cavitation only occurs in liquids."
Wouldn't Cav start to take place before the object reached the subject?
The object is already displacing air in its flight path, right?
Cavitation means that bubbles are forming and collapsing in a liquid. If you are detecting disturbance in the air, it must impose an incredible drag on the bullet. Below is the normal condition for a high speed bullet.
Aerospaceweb.org | Ask Us - Supersonic Bullet
 

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The Shadow (Moderator)
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Uuhhhhh.....
If I follow correctly, you are wanting to be able to see the supersonic disturbance, more easily? So what you are trying to do is increase the drag of the bullet, causing more "wash"???
 

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Discussion Starter #11
ok, ill call it wash from now on.

Wouldnt increased leves of wash have an altered impact on an objecr. I am obviously not a ballistics expert but am thouroghly interested in the field.
 

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The range I use has light to moderate vegitation. When I fire a factory round at a target there is very little if any disturbance in the surrounding ruffage. When I fire my modified rounds at a target there is something between a 3 to 5 foot vacuum that whips the surrounding vegitation around. I haven't documented it yet since I was a bit nervous at the first test. I will record my next test and provide a link. I am a fan of critisim. If you think I am wrong then flat out say it. I am ok with that. Otherwise. If you are near illinois we could get together and see if I am on to something.
According to the equation

Work = nRTln(V/V<sub>0</sub>)

it takes about 700,000 ft-lb to create a 4' diameter, 1/2 atm underpressure 100 yards long. Since that is several hundred times the initial energy of the bullet, something else must be taking place.
 

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Discussion Starter #13
Next test

Next time I go out to test I'll cronograph and build a psi tube, measure off test site. Dimensions and distances. I will also record it. Till then. . .
 

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The Shadow (Moderator)
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Wouldnt increased leves of wash have an altered impact on an objecr. I am obviously not a ballistics expert but am thouroghly interested in the field.
Not per se. Just because a bullet is less efficient at cutting through the air than another, doesn't mean it will do more or less damage to a target.
Now if you score the jacket enough to cause it to open upon impact, the results would be more violent more quickly. But as all of us that have had a jacket failure while hunting can tell you, it stinks and is unpredictable; other than usually flesh wounds and lost game....

Even very efficient bullets (high BC) like the 175 SMK from my 308 can be seen easily, you just need some distance. If you are trying at distances of less than 200 yards it's awfully difficult. The flight time is so short, its difficult for the eye to catch it in the scope.
 

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The Hog Whisperer (Administrator)
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You are doing this because..... ?

Understanding your goal is necessary before anyone can give useful advice.
 

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Discussion Starter #16
In short?

I guess, if I could develop a round that caused greater channeling in soft targets I could give the idea to the military and sell it to ammo mfg's. Mostly, I am trying to spice up my range time. At a dollar per pull I need to do something :)
 

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Discussion Starter #17
Range distances

To: Darkker
Where I am located, you will be lucky to find a spot that will give you 400 yards of uninterupted shooting.
 

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....I'll state that I have been furrowing a spiral pattern against the rifiling of my weapon and have noticed a significant increase in air disturbance behind the bullet. Am I chasing ghosts?

Again, thanks for the link.
You are putting a spiral pattern on the bullet that will be a drag against the bullet rotational direction? Just trying to clarify this.

Cavitation...depends on how you want to define a 'liquid'. Under the right conditions, air has water suspended in it, and I have definitely seen a vapor trail in the wake of a bullet flight (in very humid air) that is very different than just air density disturbance that is easily seen in binocs behind a shooter.
 

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Like the others, I don't think there is necessarily any correlation between destructiveness in a target and disturbance in air. It could actually be the opposite if the energy lost to the air disturbance slows the bullet too much. I also don't think the disturbance is result of a vacuum, per se. Assuming the bullet is supersonic, the main width of the disturbance would lag behind it by the time it takes for the air to spread out, perhaps giving the appearance that a vacuum is doing it.

There is a reason students of terminal ballistics have developed ballistic gelatin and other tissue simulants, and it is that nothing proves performance like getting as close as possible to actual conditions. Effect on air or even on water won't necessarily tell the tale. At the least, I would be using wet newspaper stacks to get some better indication of penetration and expansion effect than air or water can give you. If it looks promising in the wet newspaper, investment in some actual ordnance gelatin may be justified.

Meanwhile, before I even did that, I would want to see what your alterations are doing to the exterior ballistics of the bullet. Fire groups with your regular bullet and with your modified bullet at around 300 yards and without changing the sight setting. If the modified ones impact much lower, then they are losing a lot of speed and you have created a short range-only bullet. If the point of impact is within, say, five inches, and the groups are not more than ten inches at that range, then you at least have a bullet that's got reasonably useful range. If the groups are big because you can't make the bullets consistently enough, then ignore that part and just find their average location to see how far they are dropping. But from your description I would take a tall target backer with me and put the bull near the top.

I don't want to discourage you. People really do come up with new designs that ammunition makers may take an interest in. Wildcat cartridges that become popular are probably the best known example. But you do need to realize that the ammunition makers have people working on that stuff full time who have the advantage of good test equipment and facilities.

Also keep in mind that the Hague Accords limit what kinds of ammunition the military can use in warfare. IIRC, military use of expanding ammunition is permissible only in counter-terrorism operations, and not in regular combat. You'll find some information on this, here.
 
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Discussion Starter #20
Flabbergasted

Thanks to everyone. I have never been on a forum with such positive and resourseful people.
I think I am staying. :) And referring.
 
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