Patent Abstract:
Gas-operated automatic and semi-automatic guns are improved by providing their barrels with unique exterior surface configurations to reduce the weight of their barrels while retaining the barrels&#39; original stiffness and to cause the barrels to dissipate heat faster.

Full Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates broadly to gas-operated automatic and semi-automatic guns, especially rifles. More particularly, it concerns the improvement of such guns by addition of unique exterior surface configurations on their barrels. 
   2. Description of the Prior Art 
   There is a need to reduce the weight of guns that soldiers carry and an equally critical need to increase the endurance of the guns. Soldiers, especially those within the Special Operations Command, now fire their weapons much more than in the past and have actually gotten the guns so hot that projectiles will come thru the side of the hot barrels during prolonged gun battles. A serious problem gun designers must face, therefore, is how to both reduce the weight of barrels in guns without damaging their strength and also have them dissipate the heat faster so they can withstand as many as 500 rounds of continuous fire without a projectile exiting the side of the barrel. 
   It is known to create depressions in the outside walls of gun barrels to improve their strength, weight and accuracy, e.g., see U.S. Pat. No. 6,324,780. 
   It is also known that heat transfer through tube walls can be improved by creating rows of concave depressions on the outsides of the tube walls, e.g., see U.S. Pat. Nos. 5,577,555 and 5,992,512. 
   The present invention provides further advancements in weight reduction and heat release from barrels of gas-operated automatic and semi-automatic guns, especially rifles. 
   OBJECTS 
   A principal object of the invention is the provision of improvements in construction of gas-operated automatic and semi-automatic guns, especially rifles, by providing their barrels with unique exterior surface configurations. 
   Further objects include:
         1. The modification of gas-operated automatic and semi-automatic guns to reduce the weight of their barrels while retaining the barrels&#39; original stiffness.   2. The modification of gas-operated automatic and semi-automatic guns to make their barrels dissipate heat faster so the guns can withstand as many as 500 rounds of continuous fire without being destroyed by the projectiles moving thru the barrels.   3. The provision of improvements in guns that have particular application to the M16/M4 series of rifles.       

   Other objects and further scope of applicability of the present invention will become apparent from the detailed descriptions given herein; it should be understood, however, that the detailed descriptions, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent from such descriptions. 
   SUMMARY OF THE INVENTION 
   The stated objects are accomplished in accordance with the invention by providing gas-operated automatic or semi-automatic guns with a barrel having a muzzle section defined by a muzzle peripheral surface and a breech section defined by a breech peripheral surface with unique exterior surface configurations on one or both of the peripheral surfaces of the muzzle and breech sections. 
   In accordance with the invention, the breech section and/or muzzle section of the gun barrel has a longitudinal portion P of its peripheral surface encircled with an array of concave depressions each defined by a depression opening, selected from circular openings and oblong openings, of predetermined area machined in the peripheral surface and by a predetermined maximum depth. 
   In preferred embodiments of the guns of the invention, the longitudinal portion P of its breech peripheral surface has a predetermined first peripheral surface area A 1  before it is machined to reduce the weight and increase surface area. After machining, the total surface area of the longitudinal portion P of the barrel has a predetermined second peripheral surface area A 2  that includes the remaining surface area of the longitudinal portion P and the combined surface areas of the concave depressions. The ratio A 2 /A 1  advantageously is in the range 1.17 and 1.42 and this ratio depends upon the specifics of the barrel involved. This represents a 17% to 42% increase in the total surface area. 
   Where the concave depressions have circular openings all of the same size, the combined total surface area of the concave depressions A 2 CD is approximated by the equation A 2 CD=N×2πRD wherein N is the total number of concave depressions, R is the approximate radius of the circular opening of the concave depressions and D is the average predetermined depth of the depression. The remaining surface area of the longitudinal portion LP of breech peripheral surface after the concave depressions are made is approximated by the equation A 2 LP=(P×C)−(N×πR 2 ). The total surface area following the addition of the concave depressions is A 2 =A 2 CD+ 2 LP. Similar computations can be made by those skilled in the art, particularly with the assistance of computers, for muzzles of the invention having oblong opening depressions or combinations of circular opening sizes or combinations of circular and oblong opening depressions. 
   When the muzzle section is provided with concave depressions of the invention, similar surface area data and ratios apply. 
   Further, in preferred embodiments, the predetermined maximum depth of the concave depressions is between about 42% and 54% percent of the thickness of the breech section measured at the longitudinal position of the relevant concave depression. 
   The concave depressions are created in accordance with the invention by use of ball end mills or equivalent circular machining tools of selected diameter to remove a circular or oblong depression through the barrel surface and into the gun barrel to the predetermined depth. Advantageously, the concave depressions are of equal size and are arranged in honeycomb fashion. Alternative arrangements include alternate rows of two size circular depressions, oblong depressions of one size, alternate rows of two size oblong depressions and alternate rows of oblong depressions with circular depressions. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the invention can be obtained by reference to the accompanying drawings in which: 
       FIG. 1  is a sectional view of the left side of a gas operated automatic gun having a bisectional barrel with its breech section containing exterior surface configurations of the improved type provided by the invention. 
       FIG. 2  is a side elevation view of breech section of the gun shown in  FIG. 1 . 
       FIG. 3  is a side elevation of a portion of a gun barrel, with the right side partially shown in section, in accordance with the invention in which all the surface depressions therein are circular. 
       FIG. 4  is a side elevation of a portion of a gun barrel in accordance with the invention in which the surface depressions therein are a mixture of circular and oblong depressions. 
       FIG. 5  is a side elevation of a portion of a gun barrel in accordance with the invention in which all the surface depressions therein are oblong. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring in detail to the drawings beginning with  FIG. 1 , the improved gun  2  of the invention comprises a barrel  4  having a breech section  6  defined by a breech front portion  8  and a breech rear portion  10  plus a demountable and interchangeable muzzle section  12  defined by a muzzle front portion  14  and a muzzle rear portion  16 . 
   The gun  2  includes chamber  18  that is defined by a rear end  20  and front end  22 . Chamber  18  is operatively connected at its front end  22  to breech rear portion  10 . 
   The receiver  24  constitutes a major component of the gun  2 . The rear end  20  of chamber  18  is operatively mounted to receiver  24  to accept ammunition therein in known fashion. Also, an actuation cylinder  26  is mounted to the receiver  24 . 
   Located within the receiver  24  there is a mechanical system  28  operated by the actuation cylinder  26  to perform the gun functions of unlocking, extraction, ejection, feeding and relocking, 
   The breech section  6  comprises a rifled bore  30  that extends forward from the front end  22  of the chamber  18  and the muzzle section  12  comprises a smooth bore  32 . 
   An auxiliary muzzle attachment  34  is threaded onto the muzzle front portion  14 . 
   Referring now also to  FIGS. 2 &amp; 3 , the breech section  6  of barrel  4  has a longitudinal portion P of its peripheral surface  36  encircled with an array of concave depressions  38  each defined by a circular opening  40  of predetermined area machined in the peripheral surface  36  and by a predetermined maximum depth D. 
   The longitudinal portion of breech peripheral surface  36  has a first peripheral surface area prior to the addition of concave depressions  38  of A 1 =P×C, where P equals the length of the longitudinal portion P and C equals the average circumference of the peripheral surface  36  along distance P. The total surface area after the addition of concave depressions  38  is the combined total surface area of the concave depressions  38  plus the remaining surface area of the longitudinal portion of breech peripheral surface  36 . The combined total surface area of the concave depressions A 2 CD is approximated by the equation A 2 CD=N×2πRD wherein N is the total number of concave depressions  38 , R is the radius of the spherical surface of concave depressions  38  and D is the average predetermined maximum depth of the concave depressions  38 . The remaining surface area of the longitudinal portion of breech peripheral surface  36  after the concave depressions are machined is approximated by the equation A 2 LP=(P×C)−(N×πR 2 ) wherein R is the approximate average radius of the openings of concave depressions  38  at surface  36 . The total surface area following the addition of the concave depressions  38  is A 2 =A 2 CD+A 2 LP. 
   In preferred embodiments, the predetermined maximum depth D of the concave depressions  38  is between about 42% and 54% percent of the thickness T of the breech section measured at the longitudinal position of the relevant concave depression  38 . 
   Referring to  FIG. 4 , the breech section  6 A has a portion of its peripheral surface  36 A encircled with an array of concave depressions consisting of a mixture of circular concave depressions  38 A each defined by a circular opening  40 A of predetermined area machined in the peripheral surface  36 A and oblong depressions  38 B each defined by an oblong opening  40 B of predetermined area machined in the peripheral surface  36 A. 
   Referring to  FIG. 5 , the breech section  6 B has a portion of its peripheral surface  36 B encircled with an array of oblong depressions  38 B each defined by an oblong opening  40 B of predetermined area machined in the peripheral surface  36 B.

Technology Classification (CPC): 5