Terminal Ballistics Question.

[Rob228]

Here is a bit of a question for everyone. I have seen all sorts of pictures of expanded rounds of every type and have heard of and looked into all sorts of effects of bullets on tissue. What no one seems to mention in their reports is the rotation of the bullet as it passes through soft tissue. Even without using something like a Ranger T series, a fully expanded hollow point has some "petals" that sure seem like they are going to do some cutting if they keep rotating at several thousand RPM as they pass through soft tissue. This leads me to the question.

What happens to the rotation of a bullet as it passes through soft tissue?
Does the temporary wound cavity negate the effects of any cutting/tearing a rotating bullet would do?

[HiBC]

To make a very easy calculation,if we get 3000 fps and a 1 in 12 twist,its 180,000 rpm.That sounds very impressive.
Question,if,for the moment,we ignore slowing down,both in forward velocity and rotational speed,how many revolutions will the bullet make passing through a 12 in target?
Oversimplified,yes.But I think it sheds some light.

[ClayInTx]

This brings an odd thought to mind. Yeah, I fell asleep in the recliner early and am now awake at 4AM. In the hours after midnight odd thoughts come to mind that in the glare of daylight your musing does not find.

A 1 in 12 twist means the bullet rotates 360 degrees in 1 foot of travel. What if a jacketed hollow point had petals which curve to the right, looking from behind the bullet, at 30 degrees (I hope the math is right there). Then when the bullet hits tissue it would screw its way in. This is for a right hand twist, or course.

For a left hand twist the petals would need to curve the other way.

Presume the bullets come with six petals. Then we would buy cartridges like this, “I need a box of SAE .30-06 x 12 inch pitch, six right-hand thread cartridges.”

[scorpion_tyr]

As far as I understand it there is much more energy forcing the bullet forward than keeping the rotation. As soon as the bullet impacts something rotation pretty much stops. The bullet will still move and yaw around, but not enough rotation to "screw" in or to create a larger permanent cavity by the petals.

[Eagle0711]

Rob, it depends on what the bullet hits. If it hits bone, say at the base it would send it tumbling thru the body. To illustrate, if you tripped over rock while walking your upper body would continue while the bottom stopped, and you would likely tumble over.

[Rob228]

Not to bring up an older post, but I've been out of town for the past week and just now got to see the results.

Thanks for the answers, It does make sense that the resistance from the body is going to slow that spinning almost immediately. The idea of a bullet "screwing" itself in is pretty interesting though, I'm surprised none of the companies has tried to market that, either through fact or half truth.

[Brian Pfleuger]

The rotational inertia is so miniscule that no respectable company would dare mention it in advertising.

Here is an example, simplified slightly.... A .284 (7mm bullet diameter), lead cylinder 1.135 inches long with a rotational speed of 180,000 rpm has an inertia of just 0.000002066608234415381 ft.lb.^2

In other words, zero.

[LaserSpot]

The idea of a bullet "screwing" itself in is pretty interesting though, I'm surprised none of the companies has tried to market that, either through fact or half truth.

You could design a bullet with surfaces that make it spin faster when it hits. This might not make it work better, but it would be a mean looking slug.

[FrankenMauser]

Out of all the bullets I have recovered from game, reactive targets, and even dirt...

The only ones that ever appeared to stop spinning were some bullets that impacted bone, and nearly all bullets that impacted rocks (or similar solid objects).

One of my brothers even has a nice .54 caliber round ball he recovered from a deer. It penetrated more than 30 inches of body (including bone), mushroomed to over 0.750", and remained stable until it came to rest.

I have a 165 grain .30 caliber Power Point that broke both front shoulders on a doe antelope, while taking out 2 ribs, and remained stable the entire time. (It was recovered under the skin of yet another doe antelope, that had been 50+ yards behind the target. --Long story; he's lucky I tracked down the wounded one.)

I know that's not a direct answer, but it's what I've got.

As for your second question:

Does the temporary wound cavity negate the effects of any cutting/tearing a rotating bullet would do?

I don't think the actual rotation of a bullet offers any measurable increase in damage. With all of the animals I have traced wound cavities through, or recovered bullets from... I have never seen any evidence that the rotation of the bullet caused more damage. (Speaking of rotation itself -- rotation keeping the bullet stable is a different story.)

[Brian Pfleuger]

On the question of whether or not the bullet stops spinning, in the case of ballistics gel, and I would presume most any other soft material, it clearly does not. Watch this video ( or this one in WMV format) from Barnes. The effects of the rotation are clearly visible in the gel and the bullet is very obviously and clearly still spinning when it exits.

[44 AMP]

Yes, its spinning, but no, it doesn't matter. Yes, a calculation for a 3000fps bullet that comes out 180,000rpm sounds impressive, but look at the real world, and what's left out of that number.

It may be doing 180K per minute, but a bullet doesn't fly for a minute. Even very long range shots are only a few short seconds, and close range much less than that. And the time spent inside a body is even less.

Most rifle twists are around 1 in 10, give or take a few inches. Most handgun twists are much slower. Using a 1 in 10 twist means that the bullet rotates one time per 10" of travel. Even shooting someone through their thickest parts means a bullet only has time for one or at most two revolutions. Yes, an expanded bullet with "petals" looks like it would rip through like a buzz saw, but the reality is different.

[lwknight]

Any terminal ballistics tests that I ever saw were defensive tests.
Meaning a handgun at more like 1200 fps or lower and a 1:16 twist.
Talking about petals meand something akin to the golden saber or hydrashock which , again , is handgun.
Anyway , as stated earlier its not going to be like a drill with a barb on the tip.
The wound channel would not show rotation at all IMO.

[Brian Pfleuger]

Any terminal ballistics tests that I ever saw were defensive tests.
Meaning a handgun at more like 1200 fps or lower and a 1:16 twist.
Talking about petals meand something akin to the golden saber or hydrashock which , again , is handgun.
Anyway , as stated earlier its not going to be like a drill with a barb on the tip.
The wound channel would not show rotation at all IMO.

Take a look at the videos that I linked to above. Those are not defensive tests and they are high-velocity (2900fps, I believe) 308 rifle rounds.

The rotation is CLEARLY visible in the gel.

I agree that the actual damage in actual tissue will be close to non-existent and/or indistinguishable from all the other damage but the effect is clearly there in the gel.

[Rampant_Colt]

http://www.firearmstactical.com/briefs2.htm#Black-Talon

This is where the police only Winchester Ranger Talon (formerly Black Talon and Ranger SXT) bullet departs from conventional expanding hollowpoint bullets. Ranger Talon adds an additional wounding mechanism: cutting.

When Ranger Talon expands, its copper jacket peels back to form six sharp claws. These claws protrude outward just slightly beyond the smooth outer edges of the mushroom-shaped lead core shoulder.

Upon impact with flesh Ranger Talon performs identical to conventional hollowpoint bullets. However, as it penetrates and slows it does not suffer a decrease in effective bullet diameter. This is because tissue that stretches and flows around the smooth shoulder of the mushroom-shaped lead core comes into contact with the sharp copper jacket claws and is lacerated.

These lacerations contribute little to overall wound severity.

However, if Ranger Talon happens to pass very close to a major cardiovascular structure, instead of merely shoving it aside as it passes by, one of the six claws might be in position to cut the wall of this structure to cause profuse bleeding.

This additional cutting mechanism gives Ranger Talon the potential to be approximately 3% to 5% more effective than other expanding bullets of the same caliber. In one out of every 20-30 shootings, Ranger Talon might make a difference.

In order for Ranger Talon's increased wounding potential to be realized, at least two conditions must be met: 1) the bullet's wound track must pass close enough to a major blood vessel to physically touch it, and 2) one of the talons must be in the right orientation to physically contact the wall of the blood vessel as the bullet rifles past. If one of these two conditions are not met, the wound will be no more severe than any other JHP expanding bullet.

This very slight advantage could be just enough to save the life of a police officer who has to shoot a psychotic, enraged or chemically intoxicated attacker who is oblivious to being shot.

[NormW]

According to "Understanding Firearm Ballistics" by Robert Rinker. The spin of the bullet does add some damage, but a negligible amount. However, if the bullet fragments, those fragments will be thrown off at an angle from the main channel. These can obviously add additional damage.

My first post here. Didn't see an intro section. Glad to be part of the forum.

[Bud Helms]

Intro section is right there at the top of the General Discussion forum.

It's optional.

[Nnobby45]

Hmmm. I don't see any evidence of rotation, whatsoever, on the trailing "gelatin bubble"--where the twisting would be visible. If it was twisting, it would tear itself away from the bullet.

Maybe there's been too much assuming that rotation continues in gelatin and human tissue---once expansion begins. Air is one thing. A fairly dense medium is something else.

[ClayInTx]

A blonde is on one side of a river and another blonde is on the other side.

“How do you get to the other side?” asks one.

“You’re already on the other side,” says the other.

Everyone laughs except the gun forum geek.

He says, “Well, actually, in the positional relationship of the two women they really are each on the other side and the response is valid. because, you see, as one stands on one side of the river and looks......

What are you people laughing at? What’s so funny?”

[Brian Pfleuger]

Originally Posted by Nnobby45

Hmmm. I don't see any evidence of rotation, whatsoever, on the trailing "gelatin bubble"--where the twisting would be visible. If it was twisting, it would tear itself away from the bullet.

Maybe there's been too much assuming that rotation continues in gelatin and human tissue---once expansion begins. Air is one thing. A fairly dense medium is something else.

Watch the videos I linked to above. The rotation is unquestionably visible in the gel and the bullet is very obviously still spinning when it exits.

[Nnobby45]

What are you people laughing at? What’s so funny?”

Couldn't help but laugh because they remind of the blonde who was found frozen in the spring inside a drive- in movie theater. Investigators don't know for sure, but they think she went in to see "Closed for the Winter".

[ClayInTx]

As peetza points out, yes, the bullet is spinning as it exits the gelatin; look at the trail. And appears to be spinning at a good rate, too.

But I don’t believe the spin is enough to make much difference.

[RickB]

Spinning at a good rate? If the gun barrel had a 1:12 twist rate, the bullet would make one complete revolution if it penetrated 12", right? And that assumes the rotation is not slowed by the impact and subsequent penetration. I saw a video dramatization of a hollowpoint impact, and in the vid, the bullet is spinning like a little buzzsaw, but for that to be the case, the barrel would have to be threaded, rather than rifled!

[Nnobby45]

Seems like if it was spinning significantly we see test bullets with the petals bent at an angle rather than straight back.

[Dave R]

Spinning at a good rate? If the gun barrel had a 1:12 twist rate, the bullet would make one complete revolution if it penetrated 12", right?

This. If the target is 18" wide, your average pistol bullet will complete a revolution. A rifle bullet might complete 2, depending on twist. I don't think that adds a lot of lethality.

[HiBC]

I'll add some more confusion.just to think about.In the posted photos above,in the gel block,we do see a somewhat helical path,about what I would expect,it looks like rifling twist.
Maybe bullet "petal" design could influence rotation.If you fired a boat prop into water it might rotate.Bullet design could maintain rotation after the influence of the bore rifling has past.
IMO,some of expansion is like shooting a roundball from a smoothbore musket at a steel plate,and some of it is like spinning a pizza crust.
They work at the same time.It consumes rotational energy to reform the bullet.
When a spinning figure skater goes from being in tight to throwing her arms out,she slows/stops her rotation.Isn't expansion similar?
Think about recoil.In a 7 rem mag,you do feel the reaction to the linear acceleration of the bullet,but how much counter torque do you feel from the rotational acceleration?I notice the torque a little in bigbore handguns sometimes,but it is still minor compared to recoil.
And,my point is?Obleo said I did not have to have a point to have a point.
Just pondering.