Why do manufacturers make underpenetrating loads for defense?

[EvilGenius]

No, it does not have to encounter a lot of tissue to start tumbling; all that is required is to destabilize the bullet. The action that causes this is the change in density from air to human tissue. When a .223 round hits human tissue at self defense ranges, it will be traveling over 2,700 fps.

The center of mass of the bullet will be slightly behind its longitudinal center, and this means that the front of the bullet is lighter. When the round impacts human tissue, the immediate change in density will cause the bullet to slow and because the front of the bullet will slow at a faster rate because. This is what causes yawing, the rear of the bullet will end up going faster than the front and will "tumble" end over end once this destabilization occurs.

Go watch the video.

By the time it starts to destabilize and yaw it's usually already on it's way out the back of a human sized torso.

Unless you've got specialized ammo designed to destabilize earlier than a normal FMJ. Which is plenty available.

Where the horrid injuries that result from tumbling come from is entries at odd angles that send the bullet through a longer path through the body. Like if someone was prone and took a round through the shoulder or upper chest/back and heading towards the groin. They would suffer much greater injuries than someone who got hit dead square standing upright.

 

[allaroundhunter]

It isn't a video matter, it is a matter of physics.

The immediate density change is what causes the destabilization, even if the bullet does not begin to tumble until the back of the torso.

 

[Warp]

Yep penetration should be #1 so why risk it with a bullet that could clog up or worse yet fragment, shot placement while not a given can at least be worked on with training but bullet failure won't be evident until it's too late.

I bet it'll really suck to hit COM but only to have a HP stopped by Carhartt and a Hoodie and 6" of fat

FYI: When hollow points clog and fail to expand it leads to an INCREASE in penetration. Not a decrease.

I'm not sure where you are getting your misinformation.

 

[EvilGenius]

It isn't a video matter, it is a matter of physics.

The immediate density change is what causes the destabilization, even if the bullet does not begin to tumble until the back of the torso.

I wasn't arguing that it didn't, just that it doesn't happen with in a couple of inches like people think.

A lot of center mass square hits result in an exit hole not much larger than the bullet dia. because the average torso isn't thick enough to suffer from the effects of tumbling ( because by the time it starts to tumble it's already leaving) unless it's hit at an extreme angle.

 

[Warp]

No, it does not have to encounter a lot of tissue to start tumbling; all that is required is to destabilize the bullet. The action that causes this is the change in density from air to human tissue. When a .223 round hits human tissue at self defense ranges, it will be traveling over 2,700 fps.

The center of mass of the bullet will be slightly behind its longitudinal center, and this means that the front of the bullet is lighter. When the round impacts human tissue, the immediate change in density will cause the bullet to slow and because the front of the bullet will slow at a faster rate because. This is what causes yawing, the rear of the bullet will end up going faster than the front and will "tumble" end over end once this destabilization occurs.

With M193 and M855 this does not happen as reliably as users would like.

 

[allaroundhunter]

With M193 and M855 this does not happen as reliably as users would like.

No they don't, especially the M855 with its steel core. The predecessor to the M855 and M193 rounds yawed much more reliably and much earlier than the modern rounds. If one is dead-set on using FMJ for defense out of a rifle, a round with a track record for being easily upset and destabilized is the best choice.

 

[Warp]

No they don't, especially the M855 with its steel core. The predecessor to the M855 and M193 rounds yawed much more reliably and much earlier than the modern rounds. If one is dead-set on using FMJ for defense out of a rifle, a round with a track record for being easily upset and destabilized is the best choice.

What round(s) would this be, and where can they be purchased?

Just curious, I've decided on defensive .223/5.56 already for myself

 

[allaroundhunter]

Personally, I wouldn't recommend them for anyone , and I actually haven't seen any recently. The rounds that I have seen that did this best were actually old rounds that my grandfather had bought close to 20 years ago. All I remember is that they were light rounds (I think 52 gr?), but they might have been 55 gr...

I don't remember the designation for these rounds, but hopefully someone with a better memory or knowledge base than myself will come along

 

[-v-]

We all do remember that penetrating the human skin is roughly equivalent to penetrating 4" of ballistics gel as was observed by Dr. Fackler? So a 12" in gel penetration is equivalent to 8" of penetration after penetrating the skin on a frontal shot, and probably less if you have a round that hits an arm before striking COM.

Most sensible comment so far is aim for COM and vitals, and shoot as many times as it takes for the threat to stop. If they stop, sit down and contemplate the life choices they made to this point. Excellent! Threat stopped. If they stop, collapse, and create mess to clean up later. Excellent! The threat is stopped.