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Firearm with facility for open-bolt and closed-bolt operation

a technology of closed-bolt operation and open-bolt, which is applied in the field of selectfire rifles, can solve the problems of increased susceptibility to dirt and contamination entering the action and chamber, increased risk of malfunction, and less accurate aimed fire of open-bolt arms, so as to avoid the noise of bolt closure

Active Publication Date: 2010-09-23
LWRC INTERNATIONAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0003]Open bolt operation proceeds with a trigger pull causing a retracted bolt to move forward, stripping a cartridge from a magazine or belt, chambering the cartridge, and firing the cartridge. In response to firing one or more rounds, the bolt is forced back to the open position, where it is held until the trigger is pulled again. Open bolt arms have the advantage of allowing the barrel and chamber to cool more readily after sustained firing by keeping the chamber open. They avoid the risk of “cook-off,” which occurs when a cartridge is chambered into a very hot chamber, and heated to the point of ignition, causing the rifle to discharge even when the trigger is not pulled and a safety is engaged. Open bolt arms also prevent the lead core of a chambered projectile from melting away from the copper jacket, thus preventing damage to the barrel or barrel mounted sound suppressors.
[0006]Closed bolt operation, on the other hand, suffers the risk of cook-off, but enjoys the advantages of accuracy and reliability. Accuracy is provided because the bolt remains stationary up until the trigger is pulled and discharging of the cartridge has occurred. Reliability is provided because the risks of feeding the cartridge may be undertaken before the critical moment, allowing any malfunction to be addressed before encountering a threat, and because the action is closed to keep out contaminants.
[0009]Modern firearms have been disclosed that employ open and closed bolt operation. For instance, US Patent Application Publication 2007 / 0051236 to Groves et al. discloses a weapon platform that operates in open bolt mode on full auto, and closed bolt when the selector switch is set to semi-auto mode. This disclosure, incorporated herein by reference, discloses a feature of allowing the user to switch from open-bolt / full-auto mode to Semi-auto without the bolt closing, avoiding the noise of bolt closure, which may be disadvantageous in certain circumstances. Of course, this means that the rifle suffers the inaccuracy and other disadvantages of open bolt operation on the first shot from semi-auto after transitioning from open bolt auto operation.

Problems solved by technology

Open bolt arms suffer the disadvantage of increased susceptibility to dirt and contamination entering the action and chamber, because the bolt is normally open and exposes these areas to the environment.
Open bolt arms are considered less accurate for aimed fire, because the abrupt motion of the heavy bolt after trigger pull (but before discharge) tends to disrupt the aim of the firearm.
A further disadvantage of open bolt firearms is the increased risk of a malfunction at a critical moment when a first shot is needed.
This is because every step of firearm operation has some small percentage risk of failure, and open bolt firing requires not just that the cartridge properly discharge when struck by the firing pin, but that the cartridge be properly stripped, fed, and chambered, each of which has some risk of malfunction.
Of course, this means that the rifle suffers the inaccuracy and other disadvantages of open bolt operation on the first shot from semi-auto after transitioning from open bolt auto operation.
First, it is not adaptable to update or improve the many existing lower receivers (which contain the fire control group, support a grip, and receive a magazine) for these arms, and requires that an entire new lower receiver be supplied.
Second, the pivot pins employed are supported only by the relatively thin bodied aluminum, steel or polymer composite material used for the lower receiver.
The stresses generated by the reciprocating bolt that interacts with the fire control components can damagingly stretch the holes that hold the pivot pins that support the components.
Third, while the auto sear prevents discharge with the bolt out of battery, it has no safety effect to prevent out-of battery discharge when the rifle is in semi-auto mode.

Method used

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  • Firearm with facility for open-bolt and closed-bolt operation
  • Firearm with facility for open-bolt and closed-bolt operation
  • Firearm with facility for open-bolt and closed-bolt operation

Examples

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Embodiment Construction

[0016]FIG. 1 shows a select fire rifle 10 in the pattern of an M-16, AR15, M4 or AR10. The rifle has an upper receiver 12 that contains a barrel 14, and a reciprocating bolt assembly 16 (which may also be referred to as a “bolt”). The rifle has a lower receiver 20 having a grip 22, magazine well 24, and a housing portion 26 in which fire control elements reside, as will be discussed below. The barrel has a rear end 30 defining a chamber 32 into which cartridges are fed from a detachable magazine 34 during operation.

[0017]FIG. 2 shows the lower receiver 20 in greater detail, with certain conventional rifle parts omitted. The bolt assembly 16 includes a bolt 36 having a bolt head 40 that protrudes forwardly for interaction with the barrel 14. The bolt reciprocates within a bolt carrier 42. The bolt assembly reciprocates between a forward position (shown) in which the bolt head engages the chamber, and a rearward position in which the bolt head is to the rear of the magazine well, so t...

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Abstract

A firearm has a frame with a barrel connected to the frame and defining a barrel axis. The barrel has a rear end defining a chamber, and a bolt assembly reciprocates with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber. A fire control assembly includes a trigger and a selector switch with a semi-automatic position and a fully-automatic position. The fire control assembly includes a bolt assembly sear operably engaging the bolt. The fire control assembly operates when the selector switch is in the semi-automatic position in response to pulling the trigger to discharge the firearm, to load a cartridge, and to position the bolt in the closed position. The fire control assembly operates when the selector switch is in the fully-automatic position in response to pulling the trigger to discharge the firearm, and to hold the bolt in the open position. The fire control may include a sub-frame connected to the frame and to the bolt assembly sear, and may include a safety sear that prevents firing out of battery when in either full-auto or semi-auto modes. The fire control system may include a facility that momentarily maintains the trigger in a firing position when it is released while the bolt is moving forward from the open position.

Description

FIELD OF THE INVENTION[0001]This invention relates to the firearms, and more particularly to select-fire rifles.BACKGROUND AND SUMMARY OF THE INVENTION[0002]Certain firearms may operate to fire either from an open bolt configuration or a closed bolt configuration.[0003]Open bolt operation proceeds with a trigger pull causing a retracted bolt to move forward, stripping a cartridge from a magazine or belt, chambering the cartridge, and firing the cartridge. In response to firing one or more rounds, the bolt is forced back to the open position, where it is held until the trigger is pulled again. Open bolt arms have the advantage of allowing the barrel and chamber to cool more readily after sustained firing by keeping the chamber open. They avoid the risk of “cook-off,” which occurs when a cartridge is chambered into a very hot chamber, and heated to the point of ignition, causing the rifle to discharge even when the trigger is not pulled and a safety is engaged. Open bolt arms also pre...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): F41A19/33
CPCF41A17/42F41A19/44F41A19/47F41A19/46F41A19/45F41A17/16
Inventor GOMEZ, JESUS S.
Owner LWRC INTERNATIONAL
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