Topic 8 - Muzzle attachments

Question 1

what is muzzle crown deflection?

Answer 1

• The flat end of the barrel is called
  the ‘crown’.
• Any imperfection or damage to the
  crown could potentially deflect the
  bullet’s path.
• Crown damage can cause
  anomalous markings and scratches
  on the bullet with potential forensic
  significance.

Question 2

what is the noise from a muzzle?

Answer 2

The noise we hear when a gun goes off is made up of several
components from different sources:
* Pressure wave from rapidly expanding gases going
supersonic.
* Supersonic crack if the bullet goes supersonic.
* Mechanical action noise of the firearm itself
* Any other flight-related noises e.g. air friction.
* There will also be an impact sound that varies depending
on range from listener and type of projectile/target.

Question 3

what causes a pressure wave?

Answer 3

• The pressure wave is caused by the rapidly expanding
  gases produced from ignition of the propellant inside the cartridge case becoming supersonic as they leave the muzzle.

Question 4

what are suppressors?

Answer 4

• The supersonic pressure wave is generally the only sound component
  from the firearm that can be reduced by using a sound suppressor.
• Sound suppressors are commonly misnamed “silencers”, but they do
  not silence the weapon system.
• They just reduce the sound produced by supersonic gases.
• Sound suppressors can be integral to the structure of the firearm or be
  available as removable attachments.
• They may be attached by a screw thread, bayonet fitting or grub screw.

Question 5

sound suppressors part 2

Answer 5

• Considering the other sources of sound, they are relatively ineffective
  when used with supersonic ammunition.
• Supersonic bullets create their own “sonic boom”.
• However, this can make establishing directionality
  difficult as the original muzzle report will be muted,
  but the bullet’s supersonic report may echo.
• However, suppressors can be highly effective with subsonic
  ammunition.
• Legally, they are prohibited unless specified on a firearms certificate for
  a particular weapon.

Question 6

how do suppressors work to surpress sound?

Answer 6

• Sound suppressors function by slowing the gases
  leaving the muzzle.
• This is achieved by allowing expansion of the gases
  and applying turbulence to the gas flow within a
  controlled chamber (the suppressor) to slow down the
  gases to below the speed of sound upon release to
  the external environment.
• Basic components of such suppressors may include
  an expansion chamber and baffles.

Question 7

what are the types of surpressors?

Answer 7

• Can: As the name suggests, a hollow can-shaped
  extension on the muzzle: not very effective.
• Baffle: A can with partitions for the pressure wave
  to impact and transfer energy to (losing velocity).
• Reflex: A can with baffles and additional internal
  complexity, providing expansion chambers behind
  the baffles for the pressure wave to impact and
  transfer more energy to.
• Active: A reflex suppressor with spring-loaded
  baffles which further transfers the energy away
  from the pressure wave.

Question 8

how do suppressors deflect?

Answer 8

• Suppressors must be mounted concentric to the bore axis.
• If the suppressor is mounted sufficiently off axis, the bullet will strike the
  suppressor body upon exiting the barrel.
• This is usually manifested by poor accuracy, however, if the mounting is
  particularly poor, the suppressor can shatter on firing the first round with
  possibly fatal effects.
• If a suppressor has failed catastrophically the examiner must recover all
  fragments in order to reconstruct the unit.
• The bullet impact damage should be obvious once the unit has been
  reassembled.

Question 9

what is an un-proofed suppressor and what is the danger of one?

Answer 9

as well as firearms, all SUPPRESSORS MUST BE PROOF TESTED and may be certified safe for the ammunition that they are designed to be used with

e.g. a .223” round should not be used in a .22” rifle

this is because the muzzle pressure for the .223” is 50-75 times greater than for the .22”

Question 10

what are recoil reducers?

Answer 10

recoil reducers come under two main categories known as:
muzzle brakes - external and most effective
recoil compensators - integral to the firearm and less effective

they work by redirecting the propellant gases to counter the recoil of the firearm.

recoil is usually greatest for large caliber slow moving projectiles and is less for fast small caliber projectiles

Question 11

typical forms of recoil reducers?

Answer 11

a short length of tube attached at 90 degrees to the end of the barrel, diverting the gases sideways to counteract the gases normally pushing the barrel upwards.

laser cut slots in the muzzle is called magna porting.

combustion gases will typically leave the muzzle brake at an angle pointing in a rear direction, acting like a thruster on an aircraft to pull the weapon in the opposite direction to the recoil forces.

recoil reducers INCREASE THE NOISE OF THE FIREARM and the gas blast is directed back towards the firer.

they are likely to give away the shooters position on the ground.

Question 12

what are flash hiders?

Answer 12

only about 30% of a propellants chemical energy is converted into useful kinetic energy for the projectile.

the rest of energy is contained within the propellant gas particle mixture.

the very hot mixture of incandescent gases and partially burned propellant ignites in contact with the oxygen in the air causing the MUZZLE FLASH

the flash is a distinct disadvantage at night time - it also interferes with NIGHT VISION goggles.

Question 13

flash hiders part 2

Answer 13

flash hiders either:
physically hide the flash through the use of cone shaped devices.
or
by dispersing the flash upwards or sideways via a series of longitudinal cuts.

the second category is part of a dual purpose suppressor with a recoil reducer built in.

Question 14

what are grenade dischargers?

Answer 14

they are essentially a cup attached to the end of a rifle barrel into which a grenade can be launched.

or the grenade can fit straight over the barrel and be fired with bullet rounds which are caught with aluminium or steel baffle.

Question 15

what are recoil boosters?

Answer 15

very rare, can be fitted to serve a particular purpose

this being used to increase the rate of fire of short recoiling automatic weapons e.g. the MG-34 machine gun.

Question 16

what are shotgun chokes?

Answer 16

a choke - is a constriction in a shotguns barrel - used to tailor the shot pattern and can be used for different purposes.

chokes may either be formed as part of the barrel when manafactured by squeezing the end of the bore down. or by threading the barrel and screwing in an interchangeable choke tube.

the choke typically consists of a conical section that smoothly tapers from the bore diameter down to the choke diameter.

the use of interchangeable chokes has made it easy to tune the performance of a given combination of shotgun and shell to achieve the desired performance.

as the column of shot in the barrel reaches the choke in the barrel, the diameter of the shot column is reduced, thus elongating the length.

this results in the outer layers of shot in the column being given inward acceleration, delaying the spreading of the shot after leaving the barrel and reducing its dispersion.