"Holey" Bullets Claimed to Go Faster

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Discussion Overview

The discussion revolves around the claims made by an Italian weapons manufacturer regarding "holey" bullets designed to reduce drag and increase speed. Participants explore the physics behind these claims, including the effects of the holes on drag, stability, and overall performance of the bullets.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Exploratory

Main Points Raised

  • Some participants express skepticism about the design, questioning the physics of how the holes would affect drag and stability during flight.
  • One participant highlights the potential for low pressure regions created by the holes, suggesting this could lead to increased drag and noise.
  • Another participant challenges the term "rocket-like effect," proposing that it may be a marketing term rather than a scientifically valid description of the bullet's behavior.
  • There are suggestions that testing the bullets in a controlled environment could clarify their performance, though concerns about the complexity and requirements of such tests are raised.
  • Some participants argue that simply comparing the speed of a normal bullet to a holey bullet may not adequately address the claims made about performance and stability.
  • Concerns are raised about the weight of the bullets and how it may influence speed, suggesting that the holes could make the bullets lighter rather than providing any aerodynamic advantage.
  • There is a suggestion that the detailed claims made by the manufacturer may be more about marketing than scientific validity.

Areas of Agreement / Disagreement

Participants generally express skepticism about the claims made regarding the holey bullets, with multiple competing views on the implications of the design and its performance. The discussion remains unresolved, with no consensus on the validity of the claims or the best methods for testing them.

Contextual Notes

Participants note the complexity of testing bullet performance at high speeds and the potential need for advanced computational fluid dynamics (CFD) simulations. There are also concerns about the influence of weight on bullet speed and the adequacy of simple speed comparisons in validating the manufacturer's claims.

HuskyNamedNala
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Take a look at the subject article:

http://www.gizmag.com/compbullets-faster-with-vents/20806/

According to the article an Italian weapons manufacturer has designed bullets with "holes" in them which reduces their drag, muzzle flash and improve bullet speed. They claim the holes allow the combusting gunpowder to "lubricate" the bullet within the barrel thus reducing friction and increasing exit velocity.

What do you guys think?

Personally, I call BS on the design. I can't say much about the physics inside the barrel, but I am confident that as the bullet travels through the air it will create cavity drag. See http://www.eng.uwo.ca/people/esavory/cavity.htm for an explanation.

The problem is that there will be a low pressure region behind the bullet, as well as where the holes are located (this would not be the case if the holes where placed on the top portion of the nose near the body), which might lead to pressure oscillations. I would think these oscillations might increase drag and increase the "noise" of the bullet. I can't tell 100% from the pictures, but it looks like the interior of the "holes" are not rounded to facilitate smoother flow to the rear of the bullet.

I am also thinking about longitudinal stability for the first picture shown. How fast does the bullet have to rotate to maintain a stable trajectory? Do these holes move the center of gravity too far forward? Will the drag of the holes increase windage (drag due to a spinning cylinder) and thereby reduce the angular momentum?

But then again, aerodynamics and fluid mechanics is still a black art for unknown designs. May be these holes really do make a difference?
 
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HuskyNamedNala said:
The problem is that there will be a low pressure region behind the bullet
Which is supposed to be less than with a normal bullet, so it outweighs the added drag at the sides? Is that what they mean by "rocket-like effect"?
 
I have no idea what they mean by rocket-like effect. That sentence actually makes no sense physically. If they mean that the combusting gasses can travel through the bullet as it exits the muzzle, then maybe it will reduce drag and provide some thrust for the first yard outside of the barrel. I think they may have used "rocket like effect" as buzz word.

What will normally happen is you will get recirculating motion behind the bullet because it is a bluff body (at least in the rear, in the front it is streamlined). The holes would dramatically reduce this recirculation if their entrance was on the nose (similar to the intake on a car, like my 2014 Dodge Challenger :) ), but since they are on the side of the bullet, they will actually be in a region of low pressure too. Imagine 2 vacuums sucking air out of a tank.
 
Surely this is a simple matter to test, obviating any need to speculate (and risk being wrong).
 
DaveC426913 said:
Surely this is a simple matter to test, obviating any need to speculate (and risk being wrong).

I don't know about that. Say the bullet travels at Mach 1.2, you need a tunnel that can reach those speeds and a way to visualize the flow. CFD would be the cheapest option, but will require access to some serious computing power.
 
Isn't it simply a question of shooting two bullets, one normal and one holey, and see which is faster? That's the claim after all.
 
That would be the easiest test, but it wouldn't necessarily back up their more detailed claims. You would need a high speed camera at the very least. Also, weight is a contributing factor to bullet speed and acceleration. The holes may simply make the bullet lighter and achieve a higher speed during the initial flight phase without the holes doing anything beneficial. So it would also make sense to test the bullets based on weight with identical levels of powder.
 
Oh, the detailed "reasons" are just marketing fluff. I'm sure the ore they used for the bullets was first carried through the Appalachian mountains on organically fed Alpacas.
 
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HuskyNamedNala said:
The holes may simply make the bullet lighter and achieve a higher speed during the initial flight phase
Right, then you have to compare the ranges.
 
  • #10
rumborak said:
Oh, the detailed "reasons" are just marketing fluff.
Well, we all know that speed holes make cars faster:

vlcsnap-2012-11-15-16h35m30s163.png
 
  • #11
Yeah, the detailed claims can be investigated IF the gross performance proves itself out.

"Hey look, it really does go farther, faster, more accurately! Let's find out how!"
 

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