Primers and propellants Flashcards
(25 cards)
What are the two main designs of centre-fire primers?
Boxer and Berdan
Boxer was designed by British Army officer Edward Boxer, and Berdan was designed by US Army Officer Hiram Berdan.
What is the role of the anvil in a centre-fire primer?
Acts as a hard surface for the firing pin to crush the explosive compound against.
What is lead styphnate?
The most widely used initiating compound in primers.
What are the properties of lead styphnate?
- Relatively heat insensitive
- Stable in storage
- Highly sensitive to static charge
- Detonation velocity: 5200 m.s^-1
What is the typical primer charge for centre-fire and rim-fire primers?
Lead styphnate.
What is the main disadvantage of rim-fire cartridges?
Suitable only for lower energy rounds.
Define propellants.
Energetic materials which deflagrate in a controlled fashion to propel rockets or projectiles.
What is the difference between deflagration and detonation?
Deflagration is subsonic combustion; detonation is supersonic and propagates through shock.
What are the main components of black powder?
- 14% Sulphur (S)
- 10% Carbon (C)
- 76% Potassium Nitrate (KNO3 or saltpetre)
What are the problems caused by smoke from black powder combustion?
- Reveals firing position
- Obscures view of target
- Clogs gun barrel
What are the disadvantages of black powder?
- Hygroscopic
- Unstable when hot
- Highly sensitive to static
- Produces toxic by-products
What is corned gunpowder?
Black powder mixture dampened and pressed into ‘strings’ before grinding.
What was one of the biggest advancements in propellants in the 1780s?
The invention of corned gunpowder.
What is the classification of modern propellants based on?
The number of core energetic materials they contain.
What is nitrocellulose?
An energetic material created by the reaction between cellulose and nitric acid.
How does nitroglycerine compare to nitrocellulose?
More energetic and highly shock-sensitive.
What is the purpose of nitroguanidine in propellants?
Reduces muzzle flash and flame temperature.
Fill in the blank: The combustion reaction of nitroglycerine is: 4 C3H5(ONO2)3 ➞ _______.
Products include water, nitrogen, and carbon.
What are the effects of heat build-up in firearms?
- Barrel distortion
- Cook off
- Evaporation of lubricants
What is the equation relating peak chamber pressure and bore cross-sectional area?
F = P × A.
What is the significance of grain size and shape in propellants?
Affects burn rate and pressure profiles.
What are typical propellant additives?
- Reaction rate modifiers
- Flash reducers
- Wear reducers
- Stabilisers and plasticisers
- De-coppering agents
True or False: Smokeless powder produces no smoke at all.
False.
What is the combustion reaction of nitroguanidine?
H4N4CO2 → 2 H2O + 2 N2 + C.
