Measuring the lethality of hunting ammunition

The lethality of a hunting ammunition is a very complex element to characterize in the field, a large number of variables make it difficult to evaluate the performance of a projectile. (Firing angle, affected area, shooting distance, etc.) making the results non-repeatable and difficult to quantify. Fortunately, manufacturers have managed to find protocols to characterize the effectiveness of a projectile in a repeatable manner, in order to continually improve their ranges. We will explain the methodology used by them.

Part 1: A little physics

"Nothing is lost, nothing is created, everything is transformed." For Lavoisier, this law of conservation of matter is applicable to all sciences, and, of course, to ballistics.

So we will apply this notion within the framework of the “life” of a munition from internal ballistics to terminal ballistics.

1.1) Internal ballistics

Internal ballistics concerns all the physics applied to the projectile while it is still in the barrel.

This science is particularly well covered by the Quickload software (training here: https://bulletaddict.com/products/formation-quickload)

Ammunition is nothing more or less than a reservoir of chemical potential energy that is just waiting for one thing to express itself: the spark created by the primer.

This potential energy stored in the powder will be converted into 2 types of energy when fired:

• Heat energy (heat released by combustion)

• Kinetic energy (the speed brought to the projectile, it is the latter that interests us)

Chemical energy powder => Heat energy + Kinetic energy at the mouth

Please note that the efficiency of this combustion is quite low (around 25 to 35%) and depends on many factors (powder used, pressure of the ammunition, length of the barrel, etc.) When the powder burns, you will therefore transform between 25 and 35% of the chemical energy into kinetic energy and therefore waste the other part.

An analogy to the world of automobiles is possible, a gasoline engine has an optimal efficiency of around 36% when a diesel engine has efficiencies of around 42% (this is one of the reasons why a diesel engine consumes less than a gasoline engine) so respectively 36 and 42% of the energy of the fuel is used to move forward, the rest is heat that must be dissipated to avoid overheating.

Now that the projectile has left the barrel, we enter the realm of “external” ballistics.

 1.2) External ballistics

The projectile having just left the barrel, its speed will only decrease, in fact the friction of the air on the projectile will cause the projectile and the ambient air to heat up, and thus dissipate kinetic energy into heat energy.

The rate at which this kinetic energy will be lost depends on the shape of the projectile and its ability to cut through the air with the least possible friction and disturbance.

This capacity is generally described by a factor called the ballistic coefficient of the projectile (there are 2 G1 and G7, we will go into the details of these ballistic coefficients in another article).

The further away the target, the less kinetic energy there will be on impact.

So we now arrive at the moment of impact and so we will now move into the field of terminal ballistics, a science that is much more complex than the two previous ones!

  1.3) Terminal ballistics

Terminal ballistics consists of the study of the damage inflicted by a projectile, in this case a bullet.

Here we take up Lavoisier's quote: "Nothing is lost, nothing is created, everything is transformed."

The projectile will brake when it penetrates the animal; by braking, it will transform the kinetic energy into deformation energy.

If the projectile does not then come out, all of the kinetic energy has been transformed into deformation energy.

Here we are talking about deformation of a body and therefore of tissues which under the deformation will rupture and create a more or less significant hemorrhage.

What makes a good big game hunting projectile?

• Complete penetration of the animal, two holes result in larger traces on the ground to ensure finding the animal

• Maximum energy release, the exit velocity of the projectile into the animal must be very low

• The projectile must therefore conserve its mass as much as possible to guarantee good penetration.

• The release of strain energy must be maximal between 10 and 40 cm of penetration to release the energy in the vital organs.

How do manufacturers measure these parameters?

The use of 10% ballistic gel has become widespread in industry, the material allows to perfectly simulate the mechanical properties of a body. Its transparency also allows to observe the work of the projectile during penetration.

The arrival of very high-speed cameras also makes it possible to measure the speed of the projectile frame by frame and therefore to measure the braking of the projectile point by point. This makes it possible to ensure a good release of energy at the right depth.

Example: XRG ball from Solognac VS SPCE ball from Solognac

How does a hunting bullet work?

The tissues are composed of 80% water, when the projectile penetrates, the force exerted by the fluid on the projectile will tend to deform it more or less significantly depending on the architecture of the projectile.

A good hunting bullet is therefore a projectile which will deform in a controlled manner.

By deforming, the front surface of the projectile increases and therefore it will brake more quickly.

We are here on the same phenomenon as a parachute that we would open more or less wide.

• If there is too little deformation, then there is little braking and therefore little energy release: This is why an FMJ is prohibited for hunting, because the bullet is too hard and does not deform.

• If there is too much deformation then the braking will be too great, the penetration will not be good, and the energy release too early.

Lead bullets:

Conventional hunting bullets both use two materials, copper and lead. The proportion and distribution of these two materials changes the behavior of the projectile.

Copper allows:

• To provide rigidity to the projectile
• To reduce barrel fouling
• To keep, the projectile integrates at the exit of the barrel with the high rotation speeds.

Lead allows:

 

• To provide weight and therefore inertia to the projectile (high density)
• To provide flexibility to the projectile, lead is softer than copper

The dosage on the thicknesses of copper and various architectures makes it possible to control the behavior of the projectile on impact.

An FMJ on the left, followed by a "fragile" hunting bullet, followed by a hunting bullet for high penetration, followed by a monometallic bullet.

Copper bullets:

Copper or copper alloy bullets are made of a single material and therefore do not contain lead. (a controversial material due to its impact on living organisms)

But as we saw earlier, copper is much harder than lead.

So we need to find a solution to deform it on impact.

There is only one solution: create a cavity at the front of the projectile so that the fluid creates pressure in this cavity which will then open the projectile.

Two types of architectures are then possible:

Mushrooming consists of a uniform deformation, which will create a mushroom at the front of the projectile.

This mushrooming is obtained by drilling a hole of a certain diameter at the front of the projectile.

Petalization consists of a non-uniform deformation, creating petals which, with rotation, will act like blades that will cut the tissues.

This penalty is obtained by drilling a hole of a certain diameter at the front of the projectile and then forcing a square matrix (create 4 petals) or a pentagon (create 5 petals) through it.

A video in addition: