Ballistics 101: The Science of Flying Objects Bound By Gravity
Ballistics have been around since the dawn of mankind’s technological advances. Day one, when primitive man threw a rock at his dinner, the spark of marksmanship, and perfecting the trajectory of a projectile has been the mission of every marksman. From the rock, spear, atlatl, bow and arrow, to the long range precision rifle, mankind has been on the hunt to making a projectile stay in the air longer, and hit the target more accurately.
Gravity Is Constant
The main constant in ballistics will always be gravity. Gravity is the bane of ballistic science. It is what keeps us grounded, but it is the end of the road for a projectile. The theory of gravity is easy. Things that have mass pull each other. The more mass, the more gravitational pull it has. Obviously, our planet is incredibly massive. Another interesting thing about gravity on our planet, is that all things react the gravity at the same rate of acceleration. That is why, in a vacuum, all objects fall to the earth at the same rate of 9.8 m/s2 . Not to get too deep down the rabbit hole of physics and mathematical equations, but a bullet still is tied by the theory of gravity just like all other objects in a gravitational free fall.
The main difference is that a projectile also is in lateral movement. In the case of a bullet, fired from a rifle, the bullet is actively being propelled in a given direction. To keep things easy, we are going to use the example of a rifle, firing a bullet, essentially level to the target. Once a bullet is fired, it is immediately being pulled down the earth because of the constant force of gravity on all things on the planet. A bullet is not a laser beam, regardless of how great of a shot you are in video games.
What separates flatter shooting cartridges from those that seem to drop like rocks is the velocity of the bullet. The physical weight of the projectile does not directly have anything to do with the rate of drop. It indirectly is a factor only because it takes more energy to move more mass. Given the same profile of bullet, of the same caliber, and traveling at the same velocity, two bullets of different mass will actually have the same trajectory, even though they have different weights. This is an important fact in regards to ballistics, and this is also why more cartridges have been designed that don’t seem to be drastically different than older more established cartridges.
Case in point, the venerable .223 Remington/5.56 NATO cartridge. Newer cartridges have come about recently to enhance the ballistics of the .224 caliber bullet. The .22 Nosler saw some early success by being able to increase the muzzle velocity of a .224 caliber bullet. More recently, the .224 Valkyrie has become the new “speed demon” on everyone’s radar as well for a cartridge that fits inside the magwell of an AR15 rifle.
When a projectile loses velocity, it no longer covers the same amount of real-estate in the time it has before gravity ultimately brings it to a stop on the ground. The ballistic coefficient of a bullet helps to reduce its drag as it cuts through the air, which helps it to retain its velocity. The ballistic coefficient also deals with the sectional density of the bullet. Sectional density is a formula where the weight of the bullet in grains is divided by 7000. Then, that number is divided by the diameter of the bullet, squared. Sectional density does not change depending on the profile of the bullet, or style. It is a set formula that only takes into account the weight of the bullet, and the caliber. In layman’s terms, all bullets of the same weight, and the same caliber have the exact same sectional density. The reason why the bullet weight is divided by 7000, is because that is number of grains in a pound. Sectional density also has a place in terminal ballistics with how well a bullet penetrates through a game animal at a given velocity.
Bullets with a higher ballistic coefficient retain their velocity better and there is no secret as to why more and more shooters are taking up the 6mm and 6.5mm bullets for longer range shooting, and also heavier bullets. Even novice shooters with a 6.5 Creedmoor can achieve hits at 1,000 yards with minimal training, due to the great ballistics of the cartridge and flatter trajectories. The same can be said with the 6.5 Grendel out of the AR15 platform, and even bolt action rifles from Howa, and Ruger presently. Due to the science of ballistics, a cartridge like the 6.5 Grendel can achieve similar trajectories to the venerable .308 Winchester, while staying in a more compact design, and also noticeably less felt recoil. The same can be said for the .224 Valkyrie, which will be getting reviewed in the next month by yours truly. There has been a lot of hype regarding this new cartridge from Federal Premium Ammunition. Using a 90 grain Gold Medal Sierra Matchking, pushing velocities of 2700 fps at the muzzle, this tiny caliber heavy weight has earned the hype of shooters.
Stay tuned for the review of an 18” Ballistic Advantage .224 Valkyrie barrel, using Federal Premium 90 grain Gold Medal Sierra Matchkings. It will be a full review on the ammunition, the barrel, and also on a precision optic from ACME Machine!