NRA Ballistics & Ammunition 2 — Questions and Answers
Question 1: What does 'FMJ' stand for and what is its primary design characteristic?
- Full Metal Jacket — a bullet with a soft lead core enclosed in a harder metal shell (Correct answer)
- Full Magnum Jacketed — a high-pressure round with a reinforced case
- Forward Metal Jacket — a bullet with extra weight at the front for stability
- Fixed Metal Joint — a sealed primer that cannot be reloaded
Correct answer: Full Metal Jacket — a bullet with a soft lead core enclosed in a harder metal shell
FMJ (Full Metal Jacket) bullets have a soft lead core enclosed in a harder metal (usually copper or gilding metal) jacket, which reduces barrel fouling and increases penetration.
Question 2: What is 'terminal ballistics'?
- The study of how a bullet behaves inside the barrel during firing
- The study of how a projectile behaves upon impact with a target (Correct answer)
- The study of maximum range a bullet can travel
- The study of bullet trajectory during its flight
Correct answer: The study of how a projectile behaves upon impact with a target
Terminal ballistics examines what happens when a projectile strikes a target, including penetration, expansion, energy transfer, and wound channel formation.
Question 3: What is the key difference between a rimfire and a centerfire cartridge?
- Rimfire cartridges are larger in caliber than centerfire cartridges
- Rimfire cartridges have the primer compound in the rim of the case; centerfire cartridges have a separate primer in the center of the case head (Correct answer)
- Rimfire cartridges use smokeless powder while centerfire cartridges use black powder
- Rimfire cartridges are reloadable while centerfire cartridges are not
Correct answer: Rimfire cartridges have the primer compound in the rim of the case; centerfire cartridges have a separate primer in the center of the case head
In rimfire cartridges the priming compound is spun into the hollow rim of the case, while centerfire cartridges use a separate replaceable primer seated in the center of the case head.
Question 4: What is 'ballistic coefficient' (BC) and how does it affect bullet performance?
- A measure of how much a bullet expands upon impact, with higher values indicating greater expansion
- A numerical value describing a bullet's ability to overcome air resistance; higher BC means less velocity loss over distance (Correct answer)
- A rating indicating the maximum safe chamber pressure for a given cartridge
- The ratio of bullet weight to barrel twist rate required for stabilization
Correct answer: A numerical value describing a bullet's ability to overcome air resistance; higher BC means less velocity loss over distance
Ballistic coefficient is a measure of a bullet's ability to resist aerodynamic drag; a higher BC means the bullet retains velocity better over long distances.
Question 5: What causes 'keyholing,' and what does it indicate about the ammunition or firearm?
- The bullet is too heavy for the barrel twist rate, causing it to tumble and strike the target sideways (Correct answer)
- Excessive barrel heat is melting the bullet jacket, causing irregular impact patterns
- The bullet is striking the target at a steep angle due to an obstructed sight line
- A worn or damaged crown at the muzzle is causing the bullet to veer off course
Correct answer: The bullet is too heavy for the barrel twist rate, causing it to tumble and strike the target sideways
Keyholing occurs when a bullet is insufficiently stabilized by the barrel's rifling twist rate and tumbles in flight, leaving an elongated key-shaped hole in the target instead of a round hole.
Question 6: What is 'sectional density' (SD) and why is it important to hunters and instructors?
- The ratio of a bullet's diameter to its length, used to determine optimal barrel twist rate
- The ratio of a bullet's weight to the square of its diameter, indicating potential penetration capability (Correct answer)
- The measurement of how uniformly the bullet's core is distributed within the jacket
- The ratio of powder charge weight to bullet weight, used to calculate maximum pressure
Correct answer: The ratio of a bullet's weight to the square of its diameter, indicating potential penetration capability
Sectional density is the ratio of a bullet's mass to its cross-sectional area; a higher SD generally indicates better penetration, which is important in hunting to reach vital organs.
Question 7: What is 'overpressure' ammunition (indicated by '+P' or '+P+') and what precaution must an NRA instructor communicate to students?
- '+P' ammunition is loaded to lower-than-standard pressure for reduced recoil and is suitable for all firearms
- '+P' ammunition is loaded to higher-than-standard pressure for increased velocity and must only be used in firearms rated for it (Correct answer)
- '+P' ammunition uses a different primer type and is incompatible with standard firing pins
- '+P' ammunition is a military designation meaning armor-piercing and is illegal for civilian use
Correct answer: '+P' ammunition is loaded to higher-than-standard pressure for increased velocity and must only be used in firearms rated for it
+P and +P+ ammunition is loaded to pressures above SAAMI standard specifications for that caliber and should only be used in firearms specifically rated by the manufacturer to handle the extra pressure.
NRA Ballistics & Ammunition 2
What does 'FMJ' stand for and what is its primary design characteristic?