FIREARM WITH FACILITY FOR OPEN-BOLT AND CLOSED-BOLT OPERATION
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.
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This invention relates to the firearms, and more particularly to select-fire rifles.
BACKGROUND AND SUMMARY OF THE INVENTIONCertain firearms may operate to fire either from an open bolt configuration or a closed bolt configuration.
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.
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.
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.
Therefore, closed bolt firearms are generally used for semi-automatic applications, while open bolt arms tend to be used for fully-automatic applications, where accuracy is less critical, and cook-off is a greater concern.
Firearms have been developed that employ both open and closed bolt operation modes. One example is the German FG-42, a World War II era machine gun that employed select fire operation (allowing a choice of semi and full automatic) and which fired from an open bolt position during full automatic fire, and from a closed bolt position during semi-automatic operation. A change lever engages one of two sears depending on the mode of fire selected.
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.
The above disclosure suffers from several other disadvantages. 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.
The present invention overcomes the limitations of the prior art by providing a firearm having 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.
The lower receiver is essentially conventional, and formed of Aluminum or reinforced polymer. The housing portion 26 defines a chamber between opposite major sidewalls for receiving the moving parts of the fire control group. The sidewalls define a number of holes that pass entirely through the body, and these holes receive pivot pins that support the pivoting movement of various fire control components.
A hammer 44 is pivotally connected to the frame at a first pivot pin 46, and is a conventional military specification hammer. A steel trigger element 50 is pivotally attached to the frame at a second pivot pin 52, which also supports a disconnector 54. An internal subframe 56 substantially fills a rear portion of the housing chamber and supports a number of other fire control components. The subframe is formed of steel or other high-strength material that is stronger and harder than the receiver material.
The housing defines a circular selector through hole on a selector pivot axis 60 it receives a steel selector switch 62 that appears superficially conventional, except that the geometry of its internal portion is specially designed to control the function of the preferred embodiment of the invention. The housing and subframe define a through hole 64 above the selector hole, and this receives a pivot pin that supports a bolt sear element 66 and a safety sear 70. The lower receiver further defines a rear hole 72 that receives a takedown pin for attaching the upper receiver to the lower receiver. A fron hole 73 also receives a takedown pin. An elongated cylindrical plunger 74 is oriented vertically rearward of the selector, and forward of the rear takedown pin. The plunger is closely received in a bore of the subframe, for vertical reciprocation as will be discussed below. A trigger block element 76 has a lower end 80 received within a pocket 82 formed in the floor of the frame's chamber, and pivots on a horizontal pin received within a hole 84 that is drilled in the tang 86 that supports the grip handle. For newly-made receivers, as opposed to retrofitting the system into existing receivers, hole 64 in the receiver for the auto sear may be omitted, as the safety sear is supported within the sub-frame as will be illustrated below. However, this hole 64 in the receiver may also be used as a means of retention of the fire control group when the gun is taken down, such as with a spring loaded detent within the pin.
The firearm may be assembled at the time of original manufacture, or the fire control system may be installed in an existing lower receiver of an M16/M4 or AR10 pattern rifles. Much of the installation procedure is the same as with a conventional rifle, except as noted. If a conventional lower receiver is used, the pocket 82 must be wheeled into the floor of the cavity. The Tang 86 is laterally drilled to create pivot pin hole 84. The trigger block 76 is installed in the lower receiver, with a coiled spring installed below the surface 280, and the pivot pin installed in hole 84 of the receiver and hole 264 of the trigger block. The trigger, disconnector, selector and hammer are installed in a conventional manner.
The subframe is then prepared for installation by installing the reconnector plunger in through hole 150, with a retaining pin installed through subframe hole 152 and elongated plunger hole 254. Coil springs are installed in spring pockets 146 on the upper surface of the subframe, the bolt sear is positioned astride the subframe with holes 172 registered with subframe hole 140, and the safety sear is positioned with its hole 240 registered with the subframe hole 140 bolt sear holes 172. The sub-frame is then inserted into the lower receiver. The upper receiver is then mated to the lower receiver via the forward pivot/take-down pin. The upper receiver assembly is pivoted onto the lower receiver with the upper receiver rear take-down lug resting within the 142 lug retaining pocket found on 144 Sub-frame. The rear 72 take-down pin is then installed through the holes to maintain position and securing the upper, lower and sub-frame together.
Sequence of OperationsThe details of the operation of the invention are discussed below. The operation can be summarized as follows: the system may operate in a semiautomatic or fully automatic mode. In semiautomatic mode, each cycle starts and ends in a closed bolt condition. In fully automatic mode the cycle may start in either the open bolt or the closed bolt condition.
In semiautomatic mode, a conventional interaction between the trigger sear and hammer hook provide normal operation, with each shot generating the feeding of a subsequent round of ammunition. The system may be operated in fully automatic mode from several initial conditions. If the system is in a closed bolt condition with a cartridge chambered in semiautomatic mode, it may be switched to fully automatic mode. In this condition, pulling the trigger discharges the round in the chamber from a closed bolt condition, and then discharges subsequent rounds in a burst of fire that ends with the bolt in an open condition. In this condition, the bolt is ready to strip feet and fire the next round, and subsequent rounds in another burst.
When the chamber is empty and fully automatic fire is desired, the bolt may be locked back in the open position, and the rifle loaded and prepared for firing. This is the condition that would apply when a magazine is depleted under fully automatic fire, the bolt is locked back after the last shot, and the magazine is replaced with a full one when in fully automatic mode, the system may be transition back to semiautomatic mode. This would be done in circumstances in which the barrel's chamber is relatively cool, and not after extensive automatic fire. This transition might be desired to put the rifle in a condition for more accurate fire from semiautomatic mode, or to close the action to prevent incursion of dirt or debris.
It may be desirable in some circumstances to transition the system from fully automatic to semiautomatic condition, and back again, just to close the bolt and achieve the advantages of a first fully automatic shot from a closed bolt. re
Referring back to
In
This releases the hammer momentarily, until the hammer hook 182 is caught by the trigger sear 200, restraining the cocked hammer. The rotated selector allows the disconnector rear end to rise and disconnector hook 282 to move forward so that it may operate for the next semiautomatic shot in the manner discussed above. The safety sear acts as a failsafe, ensuring that the hammer will not release until the trigger is pulled and the carrier group is in full battery.
One advantage of the illustrated system is that it provides operability in the event of the failure of the carrier sear engagement surfaces 164 or 124 (i.e. sheared, rounded, or broken.) If this occurs the weapon/rifle will safely and automatically revert to closed bolt auto, thus allowing the weapon to continue operation until it can be serviced.
Additional functionality may be obtained by changing the camming surfaces on the selector to add a third mode of operation “closed bolt auto”, in which the bolt sear is restrained from engaging the bolt by a lobe on the selector, and the safety sear used to release the hammer on a closed bolt.
If the drop-in unit (Sub-frame with associated components) were to become completely damaged in the field, it could be removed by the user and the weapon will continue to operate in semi-auto mode.
Conversion back to a standard closed bolt (semi and auto) entails merely removing the trigger block, selector and drop-in unit. A standard mil-spec selector and auto sear would need to be installed. The bolt carrier group will work with the standard mil-spec fire control group
The magazine-operated last round bolt-hold open remains operable with the disclosed system both in semi-auto and open bolt modes.
While the above is discussed in terms of preferred and alternative embodiments, the invention is not intended to be so limited.
Claims
1. A firearm comprising:
- a frame;
- a barrel connected to the frame and defining a barrel axis;
- the barrel having a rear end defining a chamber;
- a bolt operable to reciprocate with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber;
- a fire control assembly including a trigger and a selector switch the fire control assembly including a bolt sear operably engaging the bolt;
- a sub-frame connected to the frame and to the bolt assembly sear;
- the selector switch including a semi-automatic position and a fully-automatic position;
- the fire control assembly being operable when the selector switch is in the semi-automatic position in response to pulling the trigger to discharge the firearm, to chamber a cartridge, and to position the bolt in the closed position;
- the fire control assembly being operable 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; and
- wherein when the bolt is held in the open position and the selector switch is in the fully-automatic position, the fire control assembly being operable in response to moving the selector switch from the fully-automatic position to the semi-automatic position to release the bolt and to feed a cartridge into the chamber.
2. The firearm of claim 1 wherein the fire control assembly is operable when the selector switch is in the semi-automatic position to limit discharging the firearm to discharging a single shot while the trigger is pulled with a sustained force.
3. The firearm of claim 1 wherein the fire control assembly is operable when the selector switch is in the fully-automatic position to repeatedly discharge the firearm while the trigger is pulled with a sustained force, and to cease discharging the firearm in response to cessation of the force on the trigger.
4. The firearm of claim 1 wherein when the bolt is held in the open position and the selector switch is in the fully-automatic position, the fire control assembly being operable in response to pulling the trigger to release the bolt from the open position, to feed a cartridge into the chamber, and to fire the cartridge.
5. (canceled)
6. The firearm of claim 1 wherein the bolt sear is movable between a disengaged position in which the bolt sear does not engage the bolt assembly, and an engaged position in which the bolt sear engages the bolt to restrain the bolt to the open position, and wherein the selector switch includes a engagement surface operable to restrain the bolt sear to the disengaged position when the selector switch is in the semi-automatic position, and to allow the bolt sear to move between the disengaged position and the engaged position when the selector switch is in the fully-automatic position.
7. The firearm of claim 1 wherein the fire control assembly includes a hammer movable between a cocked position and a released position, and a first sear operably connected to the trigger and operable to restrain the hammer in the cocked position when the selector switch is in the semi-automatic position, such that pulling the trigger releases the hammer to discharge the firearm, and wherein the bolt is operably connected to the trigger, and operable to restrain the bolt in the open position when the selector switch is in the fully-automatic position, such that pulling the trigger releases the bolt to discharge the firearm.
8. The firearm of claim 7 including a safety sear operable when the selector switch is in the fully-automatic position to restrain the hammer in the cocked position when the bolt is released, and wherein the bolt has a safety sear release element operable to contact the safety sear to release the hammer when the bolt is near the closed position.
9. The firearm of claim 7 wherein the safety sear is operable when the selector switch is in the semi-automatic position to restrain the hammer from discharging the firearm in the event the first sear fails to restrain the hammer.
10. (canceled)
11. (canceled)
12. The firearm of claim 1 wherein the subframe is formed of a stronger material than the frame.
13. The firearm of claim 12 wherein the subframe is formed of steel, and the frame is formed of aluminum.
14. A firearm comprising:
- a frame;
- a barrel connected to the frame and defining a barrel axis;
- the barrel having a rear end defining a chamber;
- a bolt assembly operable to reciprocate with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber;
- a fire control assembly including a trigger and a selector switch having a semi-automatic position and a fully-automatic position;
- the fire control assembly including a hammer movable between a cocked position and a released position;
- the fire control assembly including a first sear operably connected to the trigger and operable to restrain the hammer in the cocked position when the selector switch is in the semi-automatic position, such that pulling the trigger releases the hammer to discharge the firearm;
- the fire control assembly including a second sear operably connected to the trigger, and operable to restrain the bolt in the open position when the selector switch is in the fully-automatic position, such that pulling the trigger releases the bolt to discharge the firearm;
- the fire control assembly including a third sear operable when the selector switch is in the fully-automatic position to restrain the hammer in the cocked position when the bolt is released;
- the bolt having a release element operable to contact the third sear to release the hammer when the bolt is near the closed position; and
- the third sear being operable when the selector switch is in the semi-automatic position to restrain the hammer from discharging the firearm in the event the first sear fails to restrain the hammer when the bolt is not in the closed position.
15. The firearm of claim 14 wherein the hammer is an elongated body pivotally attached at the flame at first end, and wherein the hammer has a sear contact surface at an opposed second end operable to contact the third sear, such that the third sear restrains the hammer.
16. A firearm comprising:
- a frame;
- a barrel connected to the frame and defining a barrel axis;
- the barrel having a rear end defining a chamber;
- a bolt assembly operable to reciprocate with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber;
- a fire control assembly including a trigger and a selector switch;
- the selector switch including a semi-automatic position and a fully-automatic position;
- the fire control assembly being operable 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 being operable 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 assembly including a trigger block element operably engaged to the trigger and to the bolt to maintain the trigger in a pulled position when the selector switch is in the fully-automatic position and the trigger is released while the bolt moves forward from the open position, such that one more discharge occurs after such a release of the trigger, and the bolt does not chamber a round without discharging-it the round.
17. The firearm of claim 16 wherein the trigger block element is responsive to bolt position to determine trigger operation.
18. A firearm comprising:
- a frame;
- a barrel connected to the frame and defining a barrel axis;
- the barrel having a rear end defining a chamber;
- a bolt operable to reciprocate with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber;
- a fire control assembly including a trigger and a selector switch
- the fire control assembly including a bolt sear operably engaging the bolt;
- a sub-frame connected to the frame and to the bolt assembly sear;
- the selector switch including a semi-automatic position and a fully-automatic position;
- the fire control assembly being operable when the selector switch is in the semi-automatic position in response to pulling the trigger to discharge the firearm, to chamber a cartridge, and to position the bolt in the closed position;
- the fire control assembly being operable 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;
- wherein the fire control assembly includes a hammer movable between a cocked position and a released position, and a first sear operably connected to the trigger and operable to restrain the hammer in the cocked position when the selector switch is in the semi-automatic position, such that pulling the trigger releases the hammer to discharge the firearm, and wherein the bolt is operably connected to the trigger, and operable to restrain the bolt in the open position when the selector switch is in the fully-automatic position, such that pulling the trigger releases the bolt to discharge the firearm; and
- wherein the trigger has a first sear-engagement surface operable to restrain and release the hammer when the selector is in the semi-automatic position, and wherein the trigger has a second sear-engagement surface operable to restrain and release the hammer when the selector is in the fully-automatic position.
19. A firearm comprising:
- a frame;
- a barrel connected to the frame and defining a barrel axis;
- the barrel having a rear end defining a chamber;
- a bolt operable to reciprocate with respect to the chamber between a closed position adjacent the chamber, and an open position away from the chamber;
- a fire control assembly including a trigger and a selector switch
- the fire control assembly including a bolt sear operably engaging the bolt;
- a sub-frame connected to the frame and to the bolt assembly sear;
- the selector switch including a semi-automatic position and a fully-automatic position;
- the fire control assembly being operable when the selector switch is in the semi-automatic position in response to pulling the trigger to discharge the firearm, to chamber a cartridge, and to position the bolt in the closed position;
- the fire control assembly being operable 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;
- wherein the fire control assembly includes a hammer movable between a cocked position and a released position, and a first sear operably connected to the trigger and operable to restrain the hammer in the cocked position when the selector switch is in the semi-automatic position, such that pulling the trigger releases the hammer to discharge the firearm, and wherein the bolt is operably connected to the trigger, and operable to restrain the bolt in the open position when the selector switch is in the fully-automatic position, such that pulling the trigger releases the bolt to discharge the firearm; and
- a disconnector element operable when the selector switch is in the semi-automatic position to engage a hook on the hammer to restrain the hammer after discharge, the selector switch including a disconnector restraint surface operable when the selector switch is in the fully-automatic position to restrain the disconnector into an unengageable position in which the hammer hook does not engage the disconnector after discharge.
Type: Application
Filed: Jul 5, 2007
Publication Date: Sep 23, 2010
Applicant:
Inventor: Jesus S. Gomez (Fredericksburg, VA)
Application Number: 11/825,221
International Classification: F41A 19/33 (20060101);