Lecture Notes - lect 17

Jury Duty & Presentations

• Jury duty slots are scheduled for tomorrow afternoon, between 2 PM and 9 PM.

• Consult the FSI 5560 Moodle page for guidance.

• Presentations are approaching; group members must engage actively.

• Use Microsoft Teams for collaboration.

• Inform the instructor immediately of any group member disengagement.

• Labs continue this week: analytical and ballistics labs. Students must be prepared and know safety assessments; otherwise, they will be turned away.

Muzzle Attachments and Sound Suppressors

• Muzzle Deflection: Concerns arise if protruding metal affects the bullet's path.

• Sound suppressors work by using expansion chambers and baffles to reduce the energy of high-velocity pressure waves.

  • The pressure gas waves are reduced by interacting them with the surfaces inside of sound suppressor.

  • Reduction in energy leads to a reduction in the sound signature.

• Sound suppressors are most effective with subsonic ammunition.

  • Sound suppressors will not manage the velocity of bullets, so it's important to use subsonic ammunition for optimal sound reduction.

• Removable suppressors must be perfectly concentric with the barrel to prevent bullet impact, instability, or catastrophic failure.

• Cross-threading can cause the suppressor to be slightly misaligned, which leads to impact with the suppressor.

• Consequences of Suppressor Misalignment: Poor accuracy or fatal fragmentation.

• Forensic examiners can analyze suppressor fragments to determine impact location and compatibility.

• Caliber Considerations:

  • .22 rimfire vs. .223 centerfire cartridges, despite similar bullet diameters, have vastly different pressure levels.

  • .22 rimfire has a bullet diameter of 0.22 inches.

  • .223 has a bullet diameter of 0.223 inches.

• Weapons and suppressors undergo proofing processes to ensure ammunition compatibility.

• Using a low-pressure suppressor on a high-pressure system can be dangerous.

• Muzzle pressure of a .223 is 50-75 times greater than a .22.

Pressure{.223} = 50 \text{ to } 75 \times Pressure{.22}

• Suppressors are legally considered firearms under the 1968 Firearms Act.

• General principle: fit accessories correctly to avoid malfunction, bullet deviation, or explosion.

Recoil Reducers (Muzzle Brakes)

• Muzzle brakes reduce recoil experienced by the shooter by redirecting muzzle gases.

• High rates of fire with large weapons can cause a build up of recoil, pushing the shooter off target.

• Muzzle brakes redirect propellant gases to create forward thrust, counteracting recoil.

  • Two designs of muzzle break: circular ports (Magna ported) and larger slots to change the direction of muzzle gases

• Sound suppressors and recoil reducers serve opposite purposes.

  • Sound suppressors keep gases inside to reduce energy, while recoil reducers expel gases quickly.

• Hot gases are pushed out sideways and slightly rearwards.

• Muzzle brakes balance recoil force by thrusting the gun forward to have a calibrated system.

• Recoil reducers increase firearm noise.

Flash Hiders

• Flash hiders conceal the light signature (muzzle flash) from a firearm.

• Muzzle flash occurs when hot gases mix with oxygen after the bullet exits the barrel.

  • Hot gases contains fuel, oxygen mixes in, causing a fire type thing.

• Complete flash elimination is difficult due to the nature of combustion.

• Flash hiders either obscure the flash or expedite its dissipation.

Rifle Grenades

• Launch grenades from the end of a rifle barrel.

• Two methods exist:

  • Using blank ammunition to launch the grenade without firing a bullet

  • Using live ammunition with a bullet-catching cup to activate the grenade upon bullet impact.

• Modern grenade launchers are typically underslung, attaching below the barrel with a secondary trigger.

Recoil Boosters

• Recoil boosters increase recoil in firearms with recoil-operated mechanisms.

• Older machine guns with weaker springs used boosters to cycle the weapon.

• The MG34 is an example of a machine gun employing a recoil booster.

Shotgun Chokes

• Shotgun chokes control the spread of shotgun pellets.

• Chokes are constrictions at the end of the shotgun barrel.

• Fixed or interchangeable chokes are available.

• Chokes influence shot patterns; tighter constrictions result in focused shots.

• A choke is a constriction in the end of the shotgun barrel.

• Interchangeable chokes allow modification of constriction.

• With Choke:

  • Restriction in the end of the barrel.

  • Elongated Shot Column: The shot are pushed inward and come together for a longer, thinner channel.

  • Inward acceleration of shots occurs

• Cylinder Bore: No choke at all.

  • Full Choke: Very small constriction
    = 0.004 \text{ inches}

• Different terms indicate degree of constriction: full choke, modified choke, improved cylinder, etc.

Primers and Propellants

• Primers ignite propellant; understanding their chemistry aids forensic investigation.

• Boxer primers have a single flash hole; Berdan primers have two.

• Primer cup contains impact-sensitive mixture. Mixture is crushed against the anvil

• Boxer Primer: The anvil is built into the primer cup, which can be replaced easily.

• Berdan Primer: The anvil is built into the cartridge case, making it harder to reprime.

• Lead stiffnate is the main component of centerfire primers.
  C6 H N3 O_8 PB
  Lead(II) 4,6-trinitrobenzene-1,3-diolate

  • Energy comes from the nitro groups

  • Lead stiffnate is inexpensive and relatively easy to make.

  • The mixture causes an explosion via friction, impact, or flame.

• Mercury fulminate was a predecessor to lead stiffnate.

• Lead azide is primarily used in rimfire systems.

• Primers detonate; propellants deflagrate.

• The primer cut has the tiniest amount of explosive compound prevent damage to the firearm.

• Detonation of explosive generates heat and gas to quickly ignite propellant.

• Propellants Deflagrate: A controlled burning reaction. Subsonic event

• The deflagration propagates through thermal conductivity.

Jury Duty & Presentations

• Jury duty slots are scheduled for tomorrow afternoon, between 2 PM and 9 PM. Make sure to confirm your availability and location.

• Consult the FSI 5560 Moodle page for detailed guidance on jury duty expectations and requirements.

• Presentations are approaching; group members must engage actively and contribute equally. Regular check-ins and progress updates are essential.

• Use Microsoft Teams for collaboration. Ensure all documents and communications are centralized for easy access.

• Inform the instructor immediately of any group member disengagement or lack of participation to address issues promptly.

• Labs continue this week: analytical and ballistics labs. Students must be prepared, having reviewed all materials and safety assessments; otherwise, they will be turned away to ensure safety compliance.

Muzzle Attachments and Sound Suppressors

• Muzzle Deflection: Concerns arise if protruding metal affects the bullet's path, potentially leading to inaccurate shots. Thorough inspection and proper fitting are crucial.

• Sound suppressors work by using expansion chambers and baffles to reduce the energy of high-velocity pressure waves. The pressure gas waves are reduced by interacting them with the surfaces inside of sound suppressor, effectively diminishing the sound signature.

  • Reduction in energy leads to a reduction in the sound signature. This makes the firearm quieter but does not eliminate the sound entirely.

• Sound suppressors are most effective with subsonic ammunition. Sound suppressors will not manage the velocity of bullets, so it's important to use subsonic ammunition for optimal sound reduction to prevent the sonic boom created by supersonic rounds.

• Removable suppressors must be perfectly concentric with the barrel to prevent bullet impact, instability, or catastrophic failure. Use alignment tools to verify concentricity before use.

• Cross-threading can cause the suppressor to be slightly misaligned, which leads to impact with the suppressor. Always ensure the threads are clean and properly aligned before attaching a suppressor.

• Consequences of Suppressor Misalignment: Poor accuracy or fatal fragmentation. Misalignment can cause the bullet to destabilize or the suppressor to fail, posing significant safety risks.

• Forensic examiners can analyze suppressor fragments to determine impact location and compatibility. This analysis can reveal critical information about the cause of a suppressor failure.

• Caliber Considerations: .22 rimfire vs. .223 centerfire cartridges, despite similar bullet diameters, have vastly different pressure levels. Always use suppressors rated for the specific caliber and pressure.

  • .22 rimfire has a bullet diameter of 0.22 inches.

  • .223 has a bullet diameter of 0.223 inches.

• Weapons and suppressors undergo proofing processes to ensure ammunition compatibility and structural integrity. Regular inspections and maintenance are essential to ensure continued safe operation.

• Using a low-pressure suppressor on a high-pressure system can be dangerous, leading to suppressor failure and potential injury.

• Muzzle pressure of a .223 is 50-75 times greater than a .22. This significant difference underscores the importance of using appropriately rated suppressors.

Pressure{.223} = 50 \text{ to } 75 \times Pressure{.22}

• Suppressors are legally considered firearms under the 1968 Firearms Act, requiring registration and adherence to specific regulations.

• General principle: fit accessories correctly to avoid malfunction, bullet deviation, or explosion. Ensure all attachments are properly installed and compatible with the firearm.

Recoil Reducers (Muzzle Brakes)

• Muzzle brakes reduce recoil experienced by the shooter by redirecting muzzle gases. This helps improve accuracy and comfort, especially during rapid firing.

• High rates of fire with large weapons can cause a build up of recoil, pushing the shooter off target. Muzzle brakes mitigate this effect by stabilizing the firearm.

• Muzzle brakes redirect propellant gases to create forward thrust, counteracting recoil. Two designs of muzzle break: circular ports (Magna ported) and larger slots to change the direction of muzzle gases.

• Sound suppressors and recoil reducers serve opposite purposes. Sound suppressors keep gases inside to reduce energy, while recoil reducers expel gases quickly.

• Hot gases are pushed out sideways and slightly rearwards, creating a noticeable blast effect for those nearby.

• Muzzle brakes balance recoil force by thrusting the gun forward to have a calibrated system, allowing for more controlled and accurate follow-up shots.

• Recoil reducers increase firearm noise, making hearing protection essential when using them.

Flash Hiders

• Flash hiders conceal the light signature (muzzle flash) from a firearm, preventing the shooter's position from being easily detected in low-light conditions.

• Muzzle flash occurs when hot gases mix with oxygen after the bullet exits the barrel. Hot gases contains fuel, oxygen mixes in, causing a fire type thing.

• Complete flash elimination is difficult due to the nature of combustion, but flash hiders significantly reduce the visible flash.

• Flash hiders either obscure the flash or expedite its dissipation, employing various designs to achieve this.

Rifle Grenades

• Launch grenades from the end of a rifle barrel, providing an extended range for deploying explosive ordnance.

• Two methods exist:

  • Using blank ammunition to launch the grenade without firing a bullet, ensuring the grenade is propelled safely.

  • Using live ammunition with a bullet-catching cup to activate the grenade upon bullet impact, requiring careful aiming and handling.

• Modern grenade launchers are typically underslung, attaching below the barrel with a secondary trigger for ease of use and improved control.

Recoil Boosters

• Recoil boosters increase recoil in firearms with recoil-operated mechanisms, enhancing the reliability of cycling.

• Older machine guns with weaker springs used boosters to cycle the weapon, ensuring proper function despite design limitations.

• The MG34 is an example of a machine gun employing a recoil booster to improve its cycling rate and reliability.

Shotgun Chokes

• Shotgun chokes control the spread of shotgun pellets, allowing for different patterns depending on the intended use.

• Chokes are constrictions at the end of the shotgun barrel, influencing the pellet dispersion.

• Fixed or interchangeable chokes are available, providing versatility in shot pattern control.

• Chokes influence shot patterns; tighter constrictions result in focused shots, ideal for longer ranges.

• A choke is a constriction in the end of the shotgun barrel.

• Interchangeable chokes allow modification of constriction, adapting the shotgun to various shooting scenarios.

• With Choke:

  • Restriction in the end of the barrel.

  • Elongated Shot Column: The shot are pushed inward and come together for a longer, thinner channel, increasing range and precision.

  • Inward acceleration of shots occurs

• Cylinder Bore: No choke at all, providing the widest shot pattern for close-range targets.

  • Full Choke: Very small constriction

    = 0.004 \text{ inches}

• Different terms indicate degree of constriction: full choke, modified choke, improved cylinder, etc., each offering a different balance of range and spread.

Primers and Propellants

• Primers ignite propellant; understanding their chemistry aids forensic investigation, helping to identify ammunition types and potential modifications.

• Boxer primers have a single flash hole; Berdan primers have two, affecting their reloading process.

• Primer cup contains impact-sensitive mixture. Mixture is crushed against the anvil to initiate the explosive reaction.

• Boxer Primer: The anvil is built into the primer cup, which can be replaced easily, simplifying the reloading process.

• Berdan Primer: The anvil is built into the cartridge case, making it harder to reprime due to the fixed anvil.

• Lead stiffnate is the main component of centerfire primers.

  C6 H N3 O_8 PB

  Lead(II) 4,6-trinitrobenzene-1,3-diolate

  • Energy comes from the nitro groups

  • Lead stiffnate is inexpensive and relatively easy to make.

  • The mixture causes an explosion via friction, impact, or flame.

• Mercury fulminate was a predecessor to lead stiffnate, known for its instability and toxicity.

• Lead azide is primarily used in rimfire systems due to its sensitivity and reliable ignition.

• Primers detonate; propellants deflagrate, distinguishing their explosive and burning characteristics.

• The primer cut has the tiniest amount of explosive compound prevent damage to the firearm, ensuring controlled ignition.

• Detonation of explosive generates heat and gas to quickly ignite propellant, initiating the firing sequence.

• Propellants Deflagrate: A controlled burning reaction, producing gases to propel the bullet. A subsonic event

• The deflagration propagates through thermal conductivity, ensuring consistent and reliable burning of the propellant.