Autoloading gas port structure

A gas porting structure for an autoloading gun, wherein the structure consists of an insert fitting within a slot cut laterally thru the gun barrel and wherein one or more slot like gas ports are formed thru the insert in a longitudinal direction generally axial of the barrel.

BACKGROUND OF THE INVENTION

This invention concerns unique structure for the gas exit port in the barrel of autoloading shotguns or the like, which port exits the high pressure firing gas into the gas cylinder of the spent shell ejection system. Such gun structure is shown and described in detail in U.S. Pat. Nos. 4,693,170; 4,487,103; 4,553,469 4,654,993; and 4,893,547, the disclosures of which are hereby incorporated herein by reference in their entireties.

2. Prior Art

The above patents show the conventional gas porting structure which, for example, is designated 68 in the aforesaid U.S. Pat. No. 4,693,170 patent. Such porting is simply a slot or holes drilled thru the barrel from the outside in which leaves burs or sharp edges on the inside of the barrel. These burs and edges will naturally collect shell debris from repeated firings and restrict the proper flow of gases and also clog the gas cylinder of the ejection system and other components of the gun.

SUMMARY OF THE INVENTION

The present invention eliminates such burrs and sharp edges and debris collection by means of providing a gas porting structure comprising a relatively large lateral cut out in the barrel, and porting insert means having an overall exterior configuration conforming substantially to the overall exterior configuration of said cut out and adapted to fit into said cut out with substantial precision, wherein at least one gas port is formed laterally thru said insert means from its exterior surface thru its interior surface, and wherein the interior edge portions of said port are smooth and radiused.

DETAILED DESCRIPTION

Referring to the drawings and with particular reference to the claims herein and to the aforesaid patent U.S. Pat. No. 4,693,170, the present invention comprises a cut out generally designated10in the barrel40entering into the barrel bore29into which cut out a gas porting insert generally designated12is positioned at close dimensional tolerances, e.g., within about one to about 10 thousandths of an inch. This insert is formed with a lateral dimension “LD” and longitudinal or axial dimension “AD” and a gas porting means having one or more ports14wherein, for example for a 12 gauge shotgun, the gas flow area of each port—cross-hatched area—should be such that the total flow or cross-sectional area of all ports combined, preferably is from about 0.05 in2to about 0.12 in2. The insert structure shown, with four ports, is highly preferred as it affords an adequate gas flow rate while providing good longitudinal or axial, land (16) area on which firing debris such as shell wadding can readily slide on its way out of the barrel. Also, all of the ports are preferably formed along parallel axes a1, a2, a3and a4.

In further detail and with particular reference to the present claims and amended drawings herein, the present gas porting structure is designed for an autoloading firearm having a cylindrical barrel40having an outer cylindrical surface portion41and a cylindrical inner (bore) surface42and a discharge gas cylinder69and piston44in gas flow communication with gas porting means11provided thru the wall of said barrel and communicating directly with the bore29thereof. Piston44is affixed to a bolt carrier assembly148having a shell extractor means159, whereby flow of discharge gas into said cylinder60will force said piston44rearwardly to retract the bolt carrier assembly148, actuate the shell extractor means159and eject a shell244. The porting means generally designated11comprises a lateral cut out10completely thru a wall section of said barrel and gas porting insert means12positioned in said cut out, wherein said insert means has an outer surface13and an inner surface15formed on concentric radii17and19respectively. These radii17and19are the same (as close as possible) as outer radius21and bore radius23respectively of barrel40. Insert means12has the same length, thickness and width as said cut out and is fitted into said cut out with substantial precision whereby said inner surface15becomes a section of barrel bore29, wherein at least one gas port14is formed thru said insert means and wherein edge portions of said inner surface which outline said at least one gas port are curved such as to eliminate any sharp edge portions on which firing debris could be snagged.

The present method of providing a firearm barrel is unique as evident from the specification and drawings herein and as evidenced by the state of the art.

In the manufacture of the present insert the inside edges18of the ports, both of the sides20and ends22of the ports, are radiused and deburred by any suitable means such as machining, sand blasting or grinding or the like. This deburring is readily done on the present filly accessible insert but would be very difficult, expensive and impractical to perform on the barrels of the prior art. The radiused of the port edges, particularly of the end edges, should be large enough to offer little if any resistance to the flow of firing debris thru the barrel.

Referring to present FIG.1and to FIG. 5 of the aforesaid U.S. Pat. No. 4,693,170, the front of the gas operated antirecoil, shell ejection cylinder and the adjacent portions of the present modified barrel are shown and comprises gas cylinder and front sight28, base56, pin slots24in56gas hole70,71, gas cylinder69, gas piston44, piston rod46, guide rod43, action spring45, barrel40, pins66, pin slots26in40, gas collection chamber67and the present cut out10and insert12. It is noted that the total flow area thru chamber67should approximate the total flow area of ports14.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications will be effected with the spirit and scope of the invention.