Why Did Tubular Bullets Never Catch On?

Factual Questions
1

I understand that hollow points can be best for making large holes but most militaries avoid them because of the 1899 Hague Convention.
Tubular bullets are cones (viewed from the front, it’s a hollow circle) pushed from behind by a sabot. This allows you to make a hole that’s the same size as a normal round but with a lighter bullet, which should allow for higher velocities and/or less powder After all, if you want to make a 9mm diameter in an object, the projectile doesn’t need to be full (and therefore heavier for a given sectional density), it can just as well be a tube.

But tubular bullets never caught on even though they existed at the end of the 19th century. Any fellow gun nuts know why?

For a look, go to this PDF: http://query.nytimes.com/mem/archive-free/pdf?_r=1&res=9E06EFDE1E31E033A25756C2A9679D94659ED7CF
or here: http://guns.connect.fi/gow/peputkil.gif

2

Less mass equals less kinetic energy. In order to make a hole in someone, you want to pack as much energy into the smallest area possible. That means you want a dense material (solid lead works), not a tube.

3

I don’t know if that’s really the case - the amount of kinetic energy available comes from how much propellant is used; if you’ve got 1000J worth of powder it’ll propel a light bullet very fast or a heavy bullet more slowly.

However from an aerodynamic standpoint extra mass is important - with a higher sectional density (roughly, mass over frontal area) you get a much more stable projectile, and depending on what you’re trying to punch through at the other end, deeper penetration (even for the same KE). That’s the idea behind depleted uranium antitank rounds with a discarding sabot - a very heavy, long thin dart is very accurate and when it hits tough armor it can punch through.

So from a stability standpoint I think that’d be important with small arms. I don’t know if the small difference in diameter makes much of a difference in penetration when you’re talking about hitting soft targets (like people).

ETA - I’m sure a hollow round with a pusher or sabot or whatever is more complicated to manufacture. If it doesn’t offer a big advantage then it won’t be worth the trouble.

4

I would have thought it was momentum (velocity X mass) divided by surface area (plus the shape which is too difficult for neophytes like me to calculate) that determined how much a projectile penetrates.

As for material density, couldn’t lead plated with copper/steel/chrome/other hard material give both a high sectional density and hardness?
High energy in smallest area: The advantage of the tubular design is that it decreases the area. You can have the same energy/area ratio, still make a hole of the same diameter while requiring less energy which means less recoil and smaller and lighter rounds.

5

There’s a lot of stuff about terminal ballistics and wounding out there if you search around. I recall reading a while back that there’s a certain minimum penetration required (to reach vital organs) but beyond that it wouldn’t make a huge difference, however the overall size of the wound cavity and ability to break bones could make a big difference, the latter probably requires a lot of KE and the projectile has to hold together.

Another article said that it’s actually the length of the bullet that has a bigger impact on wound size than diameter - all bullets start to tumble when they hit and they all tend to tumble the same way, a 180 degree end-for-end turn (some studies and demonstrations were quoted to this effect). Assuming that the bullet doesn’t deform too much, a longer bullet will start to carve out a much bigger wound channel than a smaller one.

I am not an expert by a long shot (note witty pun), just what I’ve read.

6

Totally tubular, dude.

7

Ring penetrators are likely to penetrate more; they would be best used in an armor piercing capacity, because they have a higher sectional density for the same mass.

If you want wound ballistics, you want the bullet to deform as rapidly as possible once it hits the target, because that ensures the quickest and most complete transfer of energy from the projectile to the target, ensuring the most damage. A solid(ish) slug is better at energy transfer because it has more surface area to deliver energy, and it can deform better by mushrooming, causing even better energy transfer and enlarging the wound cavity.

As far as getting higher muzzle velocities with a lighter slug, it’s not a bad tradeoff – rounds have been moving that way for a while since k=mv^2/2. It’s easier to get more energy by increasing muzzle velocity than by increasing mass. However, for a given energy, recoil is the same, but pressures in the barrel and chamber can be higher. There’s also a velocity limit achievable by the propellant, though it’s probably not going to be a factor in a personal weapon.

The reason no one uses ring penetrators is because for small things, like rifles and pistols, they don’t perform better in wound ballistics, and don’t have any advantages as far as accuracy, etc, and have drawbacks like increased complexity.

For high energy armor piercing applications like tank rounds, they might have advantages, but IIRC they are harder to fin stabilize and can’t really take advantage of adiabatic shear (self-sharpening like tungsten and DU) – a KE round penetrates by sort of melting/eroding through armor, which isn’t quite the same as punching through meat or kevlar.

Really, the thing is that ring penetrators don’t solve any problems, so no one has developed them very far.

ETA: and I don’t recommend googling ring penetrator.

8

And oops: I forgot tungsten doesn’t self sharpen (from a discussion involving alternatives to DU).

9

One drawback would be that a lighter, higher velocity bullet will lose velocity and energy to air friction faster than a heavier bullet, by the same principle that lets you throw a golf ball further than you can a ping-pong ball.

Interestingly, almost the reverse of the tubular bullet you describe came into use in the '80s – The THV round, intended for police work, its reduced range is not considered a drawback, and it manages to combine good armor penetration with reduced overpenetration risk to bystanders. That armor-penetration capability, however, barred it from many US markets after the “cop-killer bullet” controversy of the same period, and it seems to have pretty much vanished.

10

I don’t think it’s the same principle. A golf ball will lose less velocity because its sectional density* is higher than a ping-pong ball. A tubular bullet has less frontal area, so you can have the same sectional density with less weight.

*Weight divided by frontal area.

Energy transfer: I don’t get the energy transfer theory of wounding. The amount of energy that is transferred by any but the most powerful weapons is not that large anyway. When someone gets shot wearing a vest, he ends up absorbing the energy yet is unharmed except for superficial injuries or a broken rib.
I thought it was the wounding channel that really incapacitated someone: you make a big hole in an organ and it won’t work so well anymore. Also, the bigger and deeper the hole you make, the more bleeding you’ll get and the more bleeding, the quicker muscles and organs (including the brain) will see their performance reduced.

Got that mainly from Martin Fackler.

11

I don’t know very much specifically about bullets, so I’ll ask some questions:

  1. Wouldn’t the tubular bullet have greater surface area, increasing its drag?

  2. Wouldn’t the tubular bullet’s reduced mass reduce it’s armor penetration?

  3. Wouldn’t there be effects of pressure from the air passing through the tube that could diminish the stability of the bullet and increase some effect at the tail end, requiring a carefully designed interior profile? If so, the best profile may have been difficult to manufacture if it was not a constant diameter bore through the center.

  4. How would imperfect manufacturing affect the stability? What if the hole were a little off center, or slightly skewed from front to back?

Finally, one thing I do know (or do know was claimed). The M1 bullet was called the ‘humane bullet’, or possibly the rifle was called the ‘humane rifle’ because its heavy round fully penetrated a victim without breaking up, but with enough force to kill. It was claimed to reduce the number of wounds that were not immediatly fatal, and kill instead of leaving an injury that would become infected (no modern anti-biotics in 1936). Would the tubular bullet have offered those supposed ‘humane’ characteristics?

12

Well, yes, that’s true. But you’re ignoring the effect of delivering that energy quickly.

Think of it this way: the kinetic energy delivered to your body from a bullet might be equal to that delivered from a nice 10mph breeze. The thing is, the breeze might take 10 hours to impart that energy, whereas a bullet can do it in a fraction of a second.

Extending the amount of time/spreading the area that energy is delivered to is how crumple zones in cars work. It’s how football pads work, how kevlar vests work, how airbags work, etc. It’s the difference between getting a tan and getting a 3rd degree burn. It’s the reason a knife can kill you but a mattress imparting the exact same amount of energy won’t even hurt you.

If you look at ballistic gel blocks, you’ll see that a bullet hitting the block makes a huge cavity which collapses to a bit larger than the diameter of the (expanded) bullet. There is a bit of controversy over the effect of a huge temporary wound cavity, but it doesn’t make a ton of sense that having a half inch hole drilled in you is just the same as having a 7 inch cavity created in your body that collapses to a half inch hole. The principle of hydrostatic shock is pretty important; that’s why a hit from a .50 caliber will remove limbs instead of simply making a .2" larger hole in you.

Incapacitation indeed occurs mostly from blood loss, but the amount of tissue damage is directly related to the speed of blood loss and accompanying shock effects. Concentrating energy into a small area and delivering that energy as fast as possible means more tissue damage, more blood loss/shock, and quicker incapacitation.

If this weren’t true, hollowpoints would be less dangerous than FMJ rounds, since they penetrate less. The principle of energy delivery is easily demonstrated with the old dry wall test; handguns with less energy penetrate further through drywall than many rifle rounds, because rifle rounds tend to deliver more energy in the first strike. But there is no question that rifles are much, much more deadly than pistols.