From the time of the initial pressure pulse when the firing pin hits the primer, to the event where the projectile hits the target....... three distinct and separate types of ballistics have taken place.
1) Internal ballistics: the science of what is happening inside the chamber and barrel from the moment of the pressure spike to the moment the bullet leaves the muzzle. Rapidly expanding gas, heat, friction, acceleration,stress, rotation, travel and exit.
2) External ballistics: the science of the external forces which act on the projectile. Gravity, wind currents, drag, temperature, altitude, humidity, angle, and even the Coriolis effect.
3) Terminal ballistics: the science of what happens when a projectile releases it's energy in a target.
Although you could be a world class shooter and not have an in depth understanding of internal, external, and terminal ballistics, having an understanding of each will empower you with the knowledge to take any shot with confidence.
How deep does one delve into the realm of becoming one with your weapon ?! Although I haven't fired a weapon in over 14 years, I started shooting at age 5. At age 18 in 1969, I was one of the highest rated shooters in the Marine Corps. I was designated to become a sniper, and took out $10,000 of extra life insurance. At the last minute, my orders were changed and I was sent to the Presidio in Monterey to study the Vietnamese language. I probably wouldn't be here today had I carried a Remington 700 in a camouflage case.
A new sniper that got in country the same day I did was sent with me to a unit in the bush. After being in country three weeks, he lost both legs from a command detonated bomb. Luckily I was just climbing out of a B52 bomb crater when the explosion happened. My head was below ground lever so the shrapnel passed over my head. I shot an M14.