Could anyone give me some proof of how long bulletrotation exists after hitting the hide of an animal (or penetrating) by a universal caliber. How far in the animal will this rotation continue? Depending on soft tissue and bones? Is there any difference between premium (strong) bullets (Barnes X, Partition) against the conventional ones as the Sierra's?
Does rotation comes to an end after hitting some weeds, leaves or twigs? In my experiments by putting a papertarget some 10 meters behind some lite obstructions, I saw accidentally ovals and keyholing, only possible if rotation has stopped. (.270 Win, 140 grains, speed 3000 fps, 220.000 rpm). Please your opinion, thanks, Jan M.

Just because the bullet is unstable dosen't mean rotation has stopped.
Good luck!

This is one of the great unanswerables. There is great argument among the self-proclaimed experts like me as to when a bullet stops spinning in an animal. I have yet to find the true answer but it may be out there. The key holes you see are due to excessive yaw, not an absence of rotation. A bullet can rotate on its own axis and exhibit yaw at the same time.

I have seen some high speed video of hollow point pistol bullets in water (nice petals show rotation very well), and the rotation seems to stop around when the forward motion does. Nothing scientific, but I would expect similar results elsewhere.

Why would the rotation suddenly stop when it hits something? To me, the logic would be that the rotation slows as velocity slows and the bullet upsets; thus, if you got a pass thru shot, the bullet would still be rotating to some extent when it exited. Wasn't some bullet's claim to fame that it produced "petals" of jacketing material that acted like a buzz saw going thru the animal?

Consider if you will that the faster the rotation stops the more rapidly the centrifigual energy would be released. Would not catastophic bullet failure result?

I agree. Tumbling in tissue occurs because the bullet doesn't spin fast enough to remain stable in tissue. Tissue is denser than air, and a rate of spin sufficient to stabilize in air is not likely to continue to stabilize in tissue.

When I look at ballistic gelatin wound channels, I can often see evidence of spinning right to the point where the bullet stops. FWIW, Dutch.

At 3000 fps a bullet in .308 calfrom a 1 in 10 twist bbl is spinning 3600 times a second, or 216,000 RPM. The rotational velocity of the surface of the bullet is 3483 fps, declining to zero as the axis of the core is reached.

If the bullet does not disintegrate when it hits something, it will be very hard to stop its spin before the forward velocity is arrested. Rapid and big expansion will make rotation slow at a faster RATE, however.

I read somewhere(?)that the Army did some testing on rotation and found that a bullet fired strait up, came back down STILL SPINNING. How they did this test, I have no idea! There is almost no resistance to the spin, as far a air, but I'm sure when it hits some meat there would be some resistance.... how much?


just my two cents

Additional Comment:
Rotation of the bullet really does not have much effect on the animal as the bullet does not rotate too many times in the short distance it travels in an animal. If you figure 1 turn in 10 inches for the average rifle, you can see that with a side on shot, the bullet probably only rotates 2 or 3 revolutions at most. People who picture a bullet acting like a ripsaw through flesh are kidding themselves. That is what makes taking Bullets like the Black Talon off the market so ridiculous.

Dutch,
I was under the impression that once the bullet had expanded it travelled in reverse due to the larger drag caused by the mushroom!

griff

Griff, here is what I understand:

Bullets must be spun to be stable because their center of gravity is behind the geometric center of the bullet. In tissue, those bullets "tumble", but really, all they do is flip over to a base first orientation. Again, this is because of the rearward center of gravity.

A mushrooming bullet is an interesting animal, because the mushroom changes the geometry of a bullet, and could well be that the center of gravity is now FORWARD of the geometric center of the bullet. Ergo, there is no overturning moment (i.e. the urge of the bullet to tumble is gone). In theory, at least, bullets with heavy mushrooms should shoot straighter through animals and make better wound channels. FWIW, Dutch.

If the bullets still had any significant velocity and turned around after impact, the mushroom edges would catch and bend back forward. I have never recovered a uniformly mushroomed bullet with the edges bent anywhere but back toward the base. I have recovered a few where one side of the jacket had split to the base, which leads me to believe that it was turning after impact and instead of a uniform peelback of the jacket, the side took the forward drag and peeled off....but that is my personal assesment.

The amount of rotational energy in a bullet is very low in relation to the total energy of a bullets kinetic energy. This can be proven. Check out the book "Understanding Firearms Ballistics" by Robert Rinker for a detailed examination.
I would hypothesize that since the amount of energy is so low -something on the order of 1/4 of 1 % that most of the rotational energy is lost soon if not immediately after impact.......DJ

Thank you all for the input. It's a difficult question, your answers were different! Who scores highest?