This invention relates to an M249 machine gun including a select fire mechanism that permits the gun to be selectively operated to be either fully automatic or semi automatic.
This invention provides a select fire mechanism for an M249 automatic rifle that permits the rifle to be operated to be either fully automatic or semi-automatic. The trigger assembly of this invention replaces what would be the typical trigger assembly of the M249, which effects fully automatic fire. The replacement of the standard M249 trigger assembly with the trigger assembly of this invention permits the rifle to be operated to be either fully automatic or semi-automatic according a selection made by the shooter.
In the M249 fully automatic rifle, the sear, which is part of the trigger assembly, holds back a spring-loaded operation rod assembly (herein “op rod assembly”), which is retained in the receiver, and pulling on the trigger pulls the sear out of engagement with the op rod assembly, thus permitting the op rod assembly to move under the influence of the spring acting upon the op rod assembly. Once released, the op rod moves forward and cycles internal striking mechanisms that cause a cartridge to be fired. Thereafter, expanding gases from the ignition of powder in the cartridge furnish the energy for the continued fully automatic operation or cycling of the rifle.
Immediately after firing, as the bullet traverses the barrel and passes an internal gas port prior to exiting from the muzzle, the live gases expand through appropriate ports to force the op rod assembly back against the bias of the spring that forces the op rod assembly toward the cartridge chamber. This loads the spring, and, once the pressure of the expanding gases dissipates, the spring again forces the op rod assembly forward to fire another round. So long as the trigger remains pulled, the sear remains out of the path of the op rod assembly, and the rifle continues to fire until the ammunition is exhausted. If the trigger is released, the sear moves back into the path of the op rod assembly, stopping the same and holding it in a spring-loaded position from which it can fire another round upon a subsequent squeezing of the trigger.
Because fully automatic fire is not always needed and not always desired, there is a need in the art for a rifle that includes a select fire mechanism permitting the rifle to be selectively operated as a fully automatic firearm or a semi automatic firearm.
The present invention generally provides a trigger assembly fitted to a trigger housing that is adapted to engage a receiver for an M249 Assault Rifle. As known for the M249 Assault Rifle, the receiver carries an op rod assembly that reciprocates within the receiver to fire the rifle. The trigger assembly of this invention includes a sear pivotally mounted to the trigger housing, the sear providing a sear tip and a latch end. A sear spring of the trigger assembly biases the sear to pivot to position the sear tip in the path of the op rod assembly when the trigger housing is engaged with the receiver and the trigger assembly is unactuated. The trigger assembly further includes a trigger pivotally mounted to the trigger housing, and a disconnector pivotally connected to the trigger. The disconnector provides a ramped surface and a catch end that is adapted to engage the latch end of the sear. The trigger assembly further includes a select fire mechanism including a switch that is accessible outside of the trigger housing and selectively movable between a fully automatic firing position and a semi automatic firing position, and a selector body is associated with the switch. The selector body includes a fully-automatic selector surface and a semi-automatic selector surface, and moving the switch between the fully automatic firing position and the semi-automatic firing position also moves the selector body between a fully automatic firing position and a semi-automatic firing position. A disconnector spring biases the disconnector toward the sear and the selector body, and actuating the trigger assembly draws the ramped surface of the disconnector against the selector body and, when the switch is in the fully-automatic firing position, the ramped surface is drawn against the fully-automatic selector surface and, when the lever is moved to the semi-automatic firing position, the ramped surface is drawn against the semi-automatic selector surface. When the ramped surface is drawn against the fully-automatic selector surface, the catch end of the disconnector engages the latch end of the sear and pulls thereon so as to pivot the sear tip out of the path of the op rod assembly and remain out of the path until the trigger is released, and, when the ramped surface is drawn against the semi-automatic selector surface, the catch end of the disconnector engages the latch end of the sear and pulls thereon so as to pivot the sear tip out of the path of the op rod assembly and thereafter disengages such that the sear pivots on the sear spring to again extend into the path of the op rod assembly after a single firing of the M249 Assault Rifle.
In a particular embodiment, the switch is a lever connected to the selector body, and the selector body is a longitudinal member having a longitudinal axis about which the longitudinal member rotates as the lever is moved. In this particular embodiment, the selector body includes a clearance cut defining a peripheral contact surface and a clearance cut surface. The peripheral contact surface serves as the semi-automatic selector surface in this embodiment, and the clearance cut surface serves as the fully-automatic selector surface.
This invention relates to the M249 Automatic Rifle, Caliber 5.56×45 mm, including known model variations. Particularly it relates to the conversion of an M249 to provide the same with a mechanism to selectively cause the rifle to fire in either a fully automatic or semi-automatic mode. This “conversion” may be in the form of replacing the trigger assembly of an M249 with a trigger assembly in accordance with this invention, or might be in the form of creating an M249 from scratch having select fire capabilities.
In the present invention, a select fire trigger assembly provides the desired select fire mechanism. Relevant portions of the select fire trigger assembly are shown in
The select fire trigger assembly 140 includes a trigger 142 that is pivotally carried on a trigger pin 144. The crescent portion of the trigger 142 is below the pivot point established by the trigger pin 144, but the body of the trigger 142 extends above that pivot point to interact with a disconnector 146 pivotally secured to the trigger 142 by a disconnector pin 148. The disconnector 146 is biased by a disconnector spring 150 to engage a latch end 152 of a sear 154. The disconnector spring 150 is a compression spring acting between a mount 143 on the trigger 142 and a mount 147 on the disconnector 146 and applies force between the two such that the disconnector 146 is forced against the sear 154 and/or a selector body 164. It should be noted that, in
The sear 154 is itself biased for limited rotational movement by a sear spring 156. The sear spring 156 is shown as a torsion spring, being wound about a sear spring pin 155 and having one end extending to act upon the sear 154 and another end extending to act upon a sear spring stop pin 157. Though a torsion spring is a preferred spring due to the force it can impart against the sear 154, other springs could be mounted in the trigger housing 141 to function in a similar manner. The sear 154 provides a sear tip 158 that, at rest (
The select fire trigger assembly 140 includes a select fire mechanism 160 that provides a lever 162 to be moved between a semi-automatic firing position (shown at the work “semi” in
With reference to
In
After this disconnection, the sear 154 is able to move independently of the trigger 142, under the influence of the sear spring 156, to again extend into the path 200 of the op rod assembly and catch the sear ledge as it travels back under the influence of the expanding gases from the firing of the cartridge. The selector body 164 provides a stop for the pivoting of the sear 154 under the influence of the sear spring 156, and the sear 154 returns to its rest position. At the rest position, the sear 154 can be reengaged with the trigger 142, at the disconnector 146, when the trigger 142 is released. Then the trigger 142 can be pulled again to fire another cartridge, and so on. Thus, in the semi-automatic firing position, the selector body 164 is positioned to cause a complete disengagement of the disconnector 146 from the sear 154, permitting the sear spring 156 to return the sear 154 to a position to engage the sear ledge of the op rod assembly and thus halt firing after the firing of one cartridge.
In
In accordance with this invention, a fully automatic M249 Assault Rifles in which an op rod assembly reciprocates to effect fully automatic fire during such time as a sear remains outside of the path 200 of a sear ledge of the op rod assembly can be altered with the trigger assembly as taught herein to be selectively made to operate in either fully automatic or semi-automatic modes.
This application claims the benefit of U.S. Provisional Patent Application No. 61/302,335, filed on Feb. 8, 2010, the contents of which are incorporated herein by reference.
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