Repeating rifle

Revision as of 14:15, 7 November 2004 by Leonard G. (talk | contribs) (Automatic Mechanism: burst mode)
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A repeating rifle is a single barreled rifle containing multiple rounds of ammunition (consisting of primer, powder, and bullet contained in a cartridge). These rounds are loaded from a reservoir chamber (magazine) by means of a manual or automatic mechanism.

Repeating rifles were a significant advance over the preceding breech loaded single shot rifles when used for military combat as they allowed a much greater rate of fire.

Manual mechanism

Revolver Action

While some early long guns were made using the revolver mechanism popular in hand guns, these did not have longevity in the marketplace. Without special sealing details the revolver mechanism produces a gas discharge close to the face when used in a long gun.

Bolt Action

The bolt closes the end of the barrel and contains the firing pin. The bolt is held in place with a lever that fits into a notch. Moving this lever out of the notch will release the restraint on the bolt, allowing it to be drawn back. An extractor removes the spent cartridge which is then ejected through the lever slot. A spring at the bottom of the magazine pushes up the reserve rounds, positioning the topmost between the bolt and the chamber at the base of the barrel. Pushing the bolt lever forward chambers this round and pushing the lever into the notch locks the bolt and enables the trigger mechanism. The complete cycle action also resets the firing pin. The Mauser rifle of the late 19th and early 20th centuries is the most famous of the bolt action types, with most similar weapons derived from this pioneering design, such as the Springfield 1903 rifle.

Lever Action

In this type, rounds are individually loaded into a tubular chamber parallel to and below the barrel. A short bolt is held in place with an over center toggle action. Once closed the over center action prevents opening solely by the force on the bolt when the weapon is fired. This toggle action is operated by a hand grip that forms part of the trigger guard. When operated, a spring in the tubular magazine pushes a fresh round into position. Returning the operating lever to the home position chambers the round and closes the breach. An interlock prevents fireing unless the toggle is fully closed. The general operation is similar to that of the bolt action described above. The famous Winchester rifle is exemplary of this type.

Automatic Mechanism

Semi-Automatic is a term used for automatic loading where each firing of the weapon requires a separate pull of the trigger. Full automatic will fire multiple rounds with a single pull. Full automatic mechanisms are employed in machine guns and this mode of operation is selectable in assault rifles. A charging lever allows the bolt to be operated to load the initial round into an empty chamber. Some automatic assault rifles are now designed to fire a limited number of rounds (typically two or three) in a quick burst. This mode of operation allows the accuracy of a single shot (since the recoil will not significantly move the rifle off of target in this short period) while increasing the kill probability due to the slight dispersion of the rounds.

Gas Operated

A portion of the gases propelling the bullet from the barrel are extracted and sent back to the rear of the rifle, where they operate a piston. The motion of this piston in turn unlocks and operates the bolt, which performs extraction of the spent cartridge and via spring action readies the next round. Almost all modern military rifles use mechanisms of this type.

Recoil Operated

In some small caliber weapons the bolt is not restrained but is relatively heavy and held against the breach by a spring. The gas pressure in the cartridge and the weapon recoil acts to push the bolt back, but owning to inertia this action does not significantly cause loss of gas pressure until after the bullet has left the barrel. Subsequent action is similar to that of the gas operated mechanism. This type of action is simple and costs little to make, but is limited in the power it can handle and so is seen on small caliber weapons.

Clip & Magazine Types

Stripper Clip

The Mauser bolt action design uses a "stripper clip", holding a number of rounds in a vertical stack. Positioning this clip between the opened bolt and the breech, the rounds are pushed down into the magazine against a spring, with the clip being discarded after the cartridges are "stripped" off.

En Bloc

Several rifle designs have relied on an "en bloc" clip design. En Bloc clips hold several cartridges under tension within a bent metal clip. The cartridges and clip are inserted as a unit into a fixed magazine within the rifle, and the clip is traditionally ejected by the rifle upon firing or chambering the final chamber. The first rifle to use an en bloc design was the M1895 Steyr-Mannlicher, and other notable en bloc fed rifles include the M1891 Paraviccini-Carcano and the US M1 Garand.

The major shortcoming of the en bloc design that prevented further adaption is that it is typically difficult or impossible to "top off" a partially loaded magazine without first cycling all unfired rounds through the action.

Box Magazine

Other designs use a pre-loaded box magazine that is inserted into a slot in the receiver of the weapon, usually from the bottom. The magazine includes a spring to elevate the rounds into position. This type of magazine is common in most modern weapons and may be straight or curved, the curve reflecting the somewhat conical shape of a high powered round, where the cartridge containing the powder is of larger diameter than the bullet.

In extreme combat situations two box magazines may be taped together with an offset, forming a reversible magazine — when the first magazine is exhausted the double clip is removed, reversed, and reinserted.

Drum Magazine

Used in the Thompson submachine gun and the "Street Sweeper" shotgun, a moving partition within a cylindrical chamber forces loose rounds into an exit slot. After loading of the magazine a key is used to wind the spring that moves the partition against the rounds. The Thompson could also use a straight box clip holding twenty rounds.

See Also