Ballistics and Trajectory

Ballistics and Trajectory

Objective: Students will define the three types of ballistics phases and discuss the effects of ballistics on the round.

Ballistics Ballistics is the science of the processes that occur from the time a firearm is fired to the time when the bullet impacts its target. Soldiers must be familiar with the principles of ballistics as they are critical in understanding how the projectiles function, perform during flight, and the actions of the bullet when it strikes the intended target. The profession of arms requires Soldiers to understand their weapons, how they operate, their functioning, and their employment. The flight path of a bullet includes three stages: the travel down the barrel, the path through the air to the target, and the actions the bullet takes upon impact with the target. These stages are defined in separate categories of ballistics; internal, external, and terminal ballistics.

Ballistics Put simply, ballistics is the study of everything that happens to the projectile from the time the primer is struck by the firing pin until the projectile comes to a complete stop. There are three phases in ballistics: 1. Internal 2. External 3. Terminal

Internal Ballistics Internal ballistics is the study of the propulsion of a projectile. Internal ballistics begin from the time the firing pin strikes the primer to the time the bullet leaves the muzzle. Once the primer is struck the priming charge ignites the propellant. The expanding gases caused by the burning propellant create pressures which push the bullet down the barrel. The bullet engages the lands and grooves (rifling) imparting a spin on the bullet that facilitates stabilization of the projectile during flight. Internal ballistics ends at shot exit, where the bullet leaves the muzzle.

Internal Ballistics

External Ballistics External ballistics is the study of the physical actions and effects of gravity, drag, and wind along the projectile s flight to the target. It includes only those general physical actions that cause the greatest change to the flight of a projectile. External ballistics begins at shot exit and continues through the moment the projectile strikes the target. External ballistics includes the path of the bullet in flight, also known as Trajectory.

External Ballistics A. Gravity and air resistance have a constant and continuous effect on a bullet passing through the air B. This constant effect causes the flight (trajectory) of the bullet to be a definitive and uniform arc. C. A common cylindrical bullet has no loft capabilities. It never rises under its own power. D. The main purpose of the spin that is imparted upon a bullet is to keep the projectile from tumbling end over end. E. A bullet fired from a true horizontal barrel begins to slow down and fall towards the earth immediately upon leaving the muzzle of the weapon.

External Ballistics A bullet flying through the air (WITHOUT WIND) is acted upon primarily by two forces, which change the direction and velocity of its motion. These two forces are: 1. Gravity, which causes the bullet to fall towards the earth 2. Air Resistance, which causes the bullet to slow down and tumble

External Ballistics We as shooters counter these forces by: 1. Increasing the angle of departure by elevating the muzzle to counter the effects of gravity 2. Imparting spin and high velocities on the bullet to counter air resistance and allow the bullet to fly in a nose forward manner at far distances. This process is very similar to throwing a football.

Trajectory To understand trajectory, you must first understand these three things: Line of Sight Line of Bore Path of the Bullet (AKA Trajectory)

Line of Sight: Trajectory Line of Sight This is what the shooter sees behind the sights and can be illustrated by drawing a straight imaginary line from your eye through the rear and front sights out to the target. This is how you aim. Line of Sight

Line of Bore: Trajectory Line of Bore This is a straight imaginary line that is drawn from the muzzle of the rifle out to the target. Line of Sight Line of Bore

Trajectory: Trajectory Path of the Bullet This is the path that the bullet will take when it is fired from the rifle. Clearly the path of this bullet does not lead to the target. What needs to change? Line of Sight Path of Bullet Line of Bore

25 meters 180 meters About 7-10 inches above LOS 300 meters Trajectory To make our bullet hit the target, we must angle the barrel up. This causes the bullet to travel in an arc. We zero the rifle so that the path of the bullet crosses our line of sight at the desired distance, in this case 300 meters. With an M4 firing standard ammunition, this causes the path of the bullet to intersect with the line of sight at 25 meters also, which is why we can begin the zeroing process with a 25 meter zero before we confirm at distance. Adjust sights Line of Sight

Trajectory POI and POA with a 300m Zero 150m/200m, about 7 in above POI 100m/250m, about 5 in above POI 50m, about 2 in above POI 50m, about 2 in below center 100m/250m, about 5 in below center 150m/200m, about 7 in below center Center Hold POI Hold for Center POI

Trajectory POI and POA with a 200m Zero 100m, about 10 in above center 250m, about 4 in above center 100m/150m, about 2 in above POI 100m/150m, about 2 in below center 250m, about 4 in below POI 300m, about 10 in below POI Center Hold POI Hold for Center POI

3 Branches of Trajectory: 1. Ascending (Rising) 2. Maximum Ordinate (Summit) 3. Descending (Falling) Trajectory

Terminal Ballistics Terminal ballistics is the science of the actions of a projectile from the time it strikes an object until it comes to rest (called terminal rest). This includes the terminal effects that take place against the target.

Terminal Ballistics

Terminal Ballistics

Terminal Ballistics Lethal Zones The Soldier s primary point of aim at any target by default is center of visible mass. This allows for a tolerance that includes the greatest margin of error with the highest probability of a first round hit. The combat conditions may require more precise fires at partially exposed targets or targets that require immediate incapacitation. Ideally, the point of aim is anywhere within a primary switch area. This point will maximize the possibility of striking major organs and vessels, rendering a clean, one shot kill.

Terminal Ballistics Hydraulic Shots Hydraulic shots, or timers, are impacts on a target where immediate incapacitation is not guaranteed. These types of ballistic trauma are termed timers as that after the strike of the bullet, the damage caused requires time for the threat to have sufficient blood loss to render it incapacitated. Hydraulic shots, although ultimately lethal, allow for the threat to function in a reduced capacity for a period of time. For hydraulic shots to eliminate the threat, they must cause a 40 percent loss of blood within the circulatory system. If the shots do not disrupt that flow at a rapid pace, the target will be able to continue its mission. Once two (2) liters of blood are lost, the target will transition into hypovolemic shock and become incapacitated.

Terminal Ballistics Circuitry Shots Circuitry shots, or switches, are strikes to a target that deliver its immediate incapacitation. Immediate incapacitation is the sudden physical or mental inability to initiate or complete any physical task. To accomplish this, the central nervous system must be destroyed by hitting the brain or spinal column. All bodily functions and voluntary actions cease when the brain is destroyed and if the spinal column is broken, all functions cease below the break.

M855 VS M855A1

M855 vs M855A1 Chamber Pressure The M855 has an average chamber pressure of 51,522 psi, which is within the 52-55,000 psi range the M4 and all 5.56mm military rifles are designed. The M855A1 is increased vastly to 61,830. In fact, you see pressure levels as high as 62,900 psi. M855

M855 VS M855A1 CHAMBER PRESSURE The increase in chamber pressure also increases the bolt velocity substantially driving the cyclic rate much faster, which increases parts wear and service life of both the bolt and the barrel M855A1

M855 vs M855A1 FEEDING PROBLEMS Due to the shape of the projectile, as well as the hardness, feeding the M855A1 through a standard GI magazine caused problems. The projectile was not introduced high enough to fully clear the feed ramps on the barrel extension causing the hard sharp tip of the projectile to damage both the upper receiver, as well as the feed ramps, and end of the barrel extension. This damage was done in just under 8,000 rounds of M855A1 usage.

FEEDING PROBLEMS cont. To correct the feeding issue the Army developed a 4th generation Enhanced Performance Magazine (EPM). The purpose of this new magazine is to change the feed angle of the feed lips to introduce the tip of the cartridge higher so the tip of the cartridge would clear the feed ramps preventing this damage. NSN 1005-01-630-9508

M855 vs M855A1 Barrier Penetration

M855 vs M855A1 Barrier Penetration This is where the M855A1 excels. Unlike the older bullet, the M855A1 s penetrator is exposed, with a sharper tip, and it weighs 19 grains, nearly twice the weight of the M855 s penetrator. And the new bullet is also pushed at a higher velocity. Fired from the M4 s 14.5-inch barrel, the penetrator can pierce 3/8 inches hardened steel at 350 meters, based on the range at which 50 percent of the rounds will pass through the barrier. That s more than twice as far as the earlier green-tipped cartridge s bullet and that distance is extended even farther when it is fired from the M16A2 s 20-inch barrel. To test those claims, both were first fired into a hardened, 3/8-inch steel plate at 100 yards; the old M855 s penetrator did not penetrate, leaving only a silver crater. The new bronze-tipped penetrator punched completely through. Next, the green-tip and bronze-tip bullets were fired at 3/8- inch soft steel at 300 yards. Again, the new bullet punched cleanly through, while the green-tipped M855 merely left a surface smear.

Trajectory POI and POA with a 300m Zero M855A1 POI 300m zero M855 POI M855 M855A1

M855 VS M855A1 TERMINAL BALLISTICS The older M855 projectile often penetrated, up to 7 inches before beginning to yaw, and will already have exited the body before yaw or fragmentation occur. According to published standards, the M855A1 is designed to yaw no more than 3 inches beyond the impact point, producing a temporary cavity diameter of 4 to 6 inches and minimum penetration depth of 12 inches, and to do that consistently.