In
breechloading
A breechloader is a firearm in which the user loads the ammunition ( cartridge or shell) via the rear (breech) end of its barrel, as opposed to a muzzleloader, which loads ammunition via the front ( muzzle).
Modern firearms are generally bre ...
firearm
A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions).
The first firearms originated in 10th-century China, when bamboo tubes ...
s, primary extraction is the initial phase (the first few millimeters) of the
extraction Extraction may refer to:
Science and technology
Biology and medicine
* Comedo extraction, a method of acne treatment
* Dental extraction, the surgical removal of a tooth from the mouth
Computing and information science
* Data extraction, the pr ...
of a spent
casing from the firearm
chamber
Chamber or the chamber may refer to:
In government and organizations
*Chamber of commerce, an organization of business owners to promote commercial interests
*Legislative chamber, in politics
*Debate chamber, the space or room that houses deliber ...
. After the primary extraction comes the secondary extraction where the bolt is moved further backwards, and the extraction is then normally finished with the spent cartridge being ejected.
The first few millimeters of extraction tend to require a much higher peak
force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a ...
than the rest of the extraction due to the spent casing sticking against the chamber walls. The sticking effect is a result from the case having expanded due to the high pressures during firing, and the extra initial force required can, depending on firearm design, make the extraction difficult for the user. Selfloading rifles usually don't have a separate motion for primary extraction, but instead depend on using a lot of force in order to start the extraction.
Different designs are used for ensuring reliable extraction in manual mechanisms, with most of them being based on the principle of
mechanical advantage
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for ...
. The camming action seen in many
bolt-action
Bolt-action is a type of manual firearm action that is operated by ''directly'' manipulating the bolt via a bolt handle, which is most commonly placed on the right-hand side of the weapon (as most users are right-handed).
Most bolt-actio ...
rifles is an example of mechanical advantage being used for chambering and extraction. There are examples of some firearm designs being less successful due to poor design around the primary extraction, which can result in a stuck case in the chamber. Notably some
pump
A pump is a device that moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy. Pumps can be classified into three major groups according to the method they ...
and
straight pull mechanisms are perceived as having the advantage over bolt actions that they are faster and require fewer body movements to operate by the user, however, they are often more complex than traditional bolt action designs, and often have little or no primary extraction
[Swiss Straight-Pull First Impressions – Forgotten Weapons](_blank)
/ref> lacking the mechanical advantage of a turn bolt which can lead to stoppages. There are some examples of straight pullBlaser R8
The Blaser R8 is a German straight-pull rifle known for its radially locking bolt system, modularity and its barrel mounted scope mount manufactured by Blaser. The rifle also features a manual cocking system and a direct trigger. In 2015 there ...
is a straight pull design which has been reported to have no issues with primary extraction.Blaser R8 , Straight-Pull Rifles Reviews , Gun Mart
/ref> In this design, the bolt head moves in a purely linear motion, and except for the bolt handle cam when opening or closing the action, operation by the shooter is also purely linear. The Heym SR 30
The Heym SR 30 is a straight-pull rifle produced in Germany by Heym. The rifle is also available in a left hand version.
Locking mechanism
The mechanism uses 6 ball bearings symmetrically positioned around the circumference of the bo ...
is another successful design which features a bolt with ball bearings as locking elements. Here the primary extraction is performed by retracting the bolt handle, which uses leverage from the opposite side of the bolt to swing the handle to the open position, giving a mechanical advantage.
See also
* List of straight-pull rifles
Straight-pull rifles differ from conventional bolt-action mechanisms in that the manipulation required from the user in order to chamber and extract a cartridge predominantly consists of a linear motion only, as opposed to a traditional turn-bolt ...
* List of pump-action rifles
A pump-action rifle is a rifle where the forend can be moved forward and backward in order to eject a spent round of ammunition and to chamber a new one. Pump-action mechanisms are often regarded as faster than a bolt action and somewhat faster ...
References
External links
Article: Primary extraction timing on Remington 700 - LongRifles, Inc.
Video: Different types of primary extraction and how they work
Video: Demonstration of primary extraction on a Remington 700
Firearm terminology