Abstract:
An improved method for producing barrels which need to operate at temperatures exceeding 800 degrees for prolonged periods of time. The method described is ideally suited for barrels which are a part of a crew served weapons, belt feed systems or other fully automatic weapons. My method has limited effect on the accuracy potential of the barrel produced and therefore should not be excluded from use on shoulder fired weapons and precision rifles.

Description:
CROSS-REFERENCED TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of PPA Ser. No. 60/899,784, filed Feb. 5, 2007 by the present inventor. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    This invention generally relates to firearms, specifically to manufacturing processes for strengthening firearm barrels to withstand temperatures exceeding 800 degrees Fahrenheit during the course of an extending firing schedule. 
         [0004]    2. Prior Art 
         [0005]    Barrels for firearms are traditionally manufactured from various allows of steel. Lining barrels with various foreign materials in order to provide resistance to corrosion, increased velocity and long service life has been a routine practice for small arms during the past 100 years. 
         [0006]    416 stainless steel has been used to prevent corrosion but is generally not as well suited for use as a firearm barrel as compared to the 4140 and 4150 chrome molly steel. 4140 and 4150 are very popular for use in military small arms such as the Colt M16. 
         [0007]    During the United States involvement in Vietnam barrel bore rusting caused weapon malfunctions. 4150 chrome molly steel barrels would rust in the humid environments. Further the small, high pressure projectile which the M16 fired eroded the chamber of the barrel rapidly. A chrome lining was applied to the barrel in order to extend the service life of the weapon. 
         [0008]    Chrome lined barrels present several problems. First it is very difficult to apply the chrome evenly for large production runs. As a result accuracy of the host weapon suffers. Chrome lining does not allow the barrel to operate at temperatures over 800 degrees for any prolonged period of time. 
         [0009]    Other ideals such as composite gun barrels as depicted in U.S. Pat. No. 6,889,464 offers a light weight alternative which cools faster than a standard barrel. Unfortunately the resins used in the construction are not suitable for sustained high rates of fire. Eventually due to high heat the resin will break down rendering the barrel unusable. 
         [0010]    Firearm barrels which are exposed to temperatures exceeding 800 degrees for a prolonged time will loose temper quickly eroding the barrel chamber. This results in the firearm malfunctioning. 
         [0011]    Other linings such as described in U.S. Pat. No. 7,197,986 are not useable with stainless steel barrels. The proposed invention of the above referenced patent does nothing to increase the strength of the barrel at higher temperatures. The coating described is limited to protecting the chamber and rifling of the barrel. When a firearm is being operated for prolong periods of time at high temperatures the temper of the barrels its self is the primary problem to over come. 
       OBJECTS AND ADVANTAGES 
       [0012]    Accordingly several objects and advantages of the present invention are
       (a) To provide a process which will enhanced corrosion resistance to both chrome moly and stainless steel barrels   (b) To provide a process which will extended barrel service life by protecting the surface of the chamber and rifling of a firearm barrel   (c) To provide a heat treat process which will allow the barrel to maintain its temper at high temperatures   (d) To provide a oxidation layer which will minimize friction between the barrel chamber and a spent cartridge   (e) To provide a oxidation layer which will reduce friction between the bore and a discharged projectile   (f) To provide a process which may be applied to a variety of steel   (g) To provide a oxidation layer around the gas port to as to extend the service life of auto loading rifles       
 
         [0020]    Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings. 
       SUMMARY 
       [0021]    This invention is in answer to the steady increase of the use of hotter burning gun powder for performance and the full automatic utilization for more rounds per minute. Both characteristics have continued to push the gun barrel life to the limit with regard to hot strength and barrel erosion. Until now, many attempts have been made to improve barrel performance with insufficient success. It is safe to say that gun barrel performance has been one of the primary limits to the increase of gun firepower. 
         [0022]    A new method for increasing gun barrel performance is disclosed herein and is more than simply a gun barrel coating or lubricant. The present invention is a simple but effective method for enhancing the performance of the gun barrel itself and introduces additional benefits noted herein. 
         [0023]    One object of the present invention is the composite hardening of the barrel. The barrel is initially hardened to HRC 50-55 after the chambering and machining process are complete. 
         [0024]    Another object of the present invention is to provide a simple but meaningful method of improving the metal of the gun barrel with a liquid salt dip nitride surface conversion which tempers the barrel steel and leave a black oxide surface layer which is extremely resistance to corrosion. This process does not add significantly to the dimensions of the barrel. 
         [0025]    While the interior and exterior of the barrel are being oxidized through the process of a liquid salt dip those same surfaces are also being heat treated to a HRC 68-72 to a depth of fifteen thousandths of an inch. 
         [0026]    The method I am describing as novel creates a core barrel hardness of HRC 50-55 and a diffusion layer about fifteen thousands deep on the interior surface of the barrel which is HRC 68-72. This diffusion layer will extend the life of the barrel as compared to popular coatings such as chrome lining. As the surface oxidation erodes the bare metal underneath is harder than the metal present under a chrome lining. 
         [0027]    My method is superior to coatings because it is actually changing the property of the barrel steel and is not limited to what types of steel may be processed. 
     
    
     
       DRAWINGS 
         [0028]    The novel features believed to be characteristic of the invention, together with further advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which a preferred embodiment of the present invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
           [0029]      FIG. 1  is a longitudinal sectional view of various layers of metal which in the preferred embodiment is a firearm barrel; 
           [0030]      FIG. 2  is a sectional side view of the preferred embodiment chamber located on a firearm barrel; 
           [0031]      FIG. 3  is a sectional side view of the muzzle on the preferred embodiment firearm barrel; 
           [0032]      FIG. 4  is a block diagram illustrating one set of steps used in making the extreme duty machine gun barrel. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0033]    As used herein, the word “front” or “forward” corresponds to the firing direction of the firearm (i.e., to the right as shown in  FIGS. 1 ,  2  and  3 ); “rear” or “rearward” or “back” corresponds to the direction opposite the firing direction of the firearm (i.e., to the left as shown in  FIGS. 1 ,  2  and  3 ); “longitudinal” means the direction along or parallel to the longitudinal axis a of the barrel of the firearm; and “transverse” means a direction perpendicular to the longitudinal direction. 
         [0034]    In  FIG. 1 , there is shown a longitudinal sectional view of a composite of harness layers of a firearm barrel  1 , which in the preferred embodiment is a M4 carbine gun barrel having a breech end  5 , a muzzle end  6 , an inner and outer black oxide surface coating  2 , and an diffusion layer  3 . In the preferred embodiment, the firearm barrel  1  is H13 tool steel or other hard refractory material such as for example 4150 carbon steel or a 400 series stainless steel. It has internal walls forming a central longitudinally extending bore  7  which may have rifling on the inside. In the preferred embodiment, the black oxide surface layer  2  comprises all surfaces which are external in that they are in contact with the external environment. The diffusion layer  3  comprises barrel  1  material which begins at a depth of one thousandth from the surface of the firearm barrel  1 . The black oxide surface layer  2  also coats the interior of the gas port  4 . 
         [0035]    In  FIGS. 2 &amp; 3 , there is shown a longitudinal sectional view of the firearm barrel  1  chamber  5  and muzzle  6 . Illustrated is the contiguous surface protection afford by the black oxide coating  2 . Also depicted is the diffusion  3  which is surrounded on all sides by the salt nitride layer. 
         [0036]    In  FIG. 4 , there is shown a flow diagram of a process  20  for producing the Noveske Rifleworks Machine Gun Barrel  1  which is designed to offer the machine gun user the option to operate the weapon at higher temperatures than normally allowed with the current machine gun barrel options. This is accomplished with the use of our proprietary barrel material, the hardening process, and the final surface conversion process. The barrel  1  is made using H13 tool steel in the softened machinable state. Once the barrel  1  has been machined  10 , the bore is hand lapped using a lead lap  11  impregnated with aluminum oxide particles to orient the land and groove surfaces with the helical twist of the rifling. This process insures that no mechanical abrasion will occur on the projectile as a result of its travel down the bore. This lapping  11  process is also a critical step for the surface conversion process which will be covered later in this description. 
         [0037]    Next, the barrel is chambered  12 , a term which describes the removal of barrel material at the rear which results in the negative of a firearm cartridge. A cartridge is the assembled unit comprised of a case, primer, propellant, and projectile. The barrel  1  now is ready for hardening. The H13 tool steel is hardened to HRC 50-55  13 . Then the barrel  1  is subjected to a unique process which is a liquid salt dip nitride surface conversion  14  which also tempers the hardened barrel  1 . The end result is a barrel  1  with a blackened oxide surface  2  which is extremely resistant to oxidation and other forms of corrosion. Also, the blackened oxide surface  2  is very slick which affects the chamber  5  by improving extraction and affects the bore by reducing friction on the projectile. The nitrided surface extends the serviceable life of the barrel  1  in that it the surface of the barrel material is transformed into a very hard and durable state, about HRC 68-72. This hardened blackened oxide surface  2  will wear slower than a coating, and is not as sensitive to fluxuations in temperature as coatings such as hard chrome. The blackened oxide surface  2 , or nitriding process hardens the surface for about one thousandth of an inch, and also hardens the material under the surface for about fifteen thousandths of an inch. This secondary layer is called the diffusion layer  3 . The diffusion layer  3  offers an extended barrel life over current hard chrome lined barrels in that as the hardened blackened oxide surface  2  layer erodes, the tooth-like portion of the bore, the lands, are still harder in their core than the core of the fore mentioned hard chrome lined barrels. The diffusion layer  3  also offers an improved resistance to corrosion than the worn and exposed barrel material used in the hard chrome lined barrel. The nitrided surface is an improvement over hard chrome in this regard in that it is not a coating, but a transformation to the existing material, (H13). This process may be applied to many types of barrel steel. 
         [0038]    Thus, there has been described a preferred method for the production of my extreme duty machine gun barrel. My method prepares a barrel  1  to operate at temperatures up to 1000 degrees with out fear of the barrel  1  loosing its temper. The bore  7  and chamber  5  of the barrel will resist erosion from the high heat and pressure producing a barrel with superior duty cycle over other barrels which are coated with chrome or manufactured using other currently available methods. My method of machining  1  the lands and grooves of the barrel, heat treating the base barrel material to provide a HRC 50-55  13 , and finally salt nitride dipping  14  the barrel to provide a surface and diffusion layer which is HRC 68-72 and resistant to corrosion may be adapted to work with stainless steel and other tool steels commonly available such as 4140 and 4130 chrome moly. Other embodiments of the present invention, and variations of the embodiment described herein, may be developed without departing from the essential characteristics thereof. Accordingly, the invention should be limited only by the scope of the claims listed below. 
       CONCLUSION, RAMIFICATIONS, AND SCOPE 
       [0039]    Accordingly the reader will see that, according to the invention, I have provided a barrel which is capable of extended duty cycles were temperatures may exceed 800 degrees Fahrenheit. Further is can bee seen that my process of manufacture and method of production may be applied to a wide variety of metals which are suitable for use as firearms barrel. I have also afforded the user of barrels produced by my method the opportunity to use their firearms for firing schedules which would destroy or significantly reduce the useful life of other currently available barrel. 
         [0040]    While my above drawings and description contain many specificities, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. 
         [0041]    Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.”