Magnesium firearm forearm and method of manufacture

Abstract

A forearm for a firearm that includes a magnesium alloy body. The forearm can be adapted for use in a modular rifle having both an upper receiver securable to a barrel and a lower receiver housing a trigger assembly. The magnesium body may also be nickel plated and have a ceramic coating on the nickel plating. Also disclosed are methods of manufacturing a forearm having a magnesium alloy body. The magnesium alloy body may be formed by extrusion or by thixotropic molding. In some embodiments, the magnesium forearm includes an outer sleeve formed out of a magnesium alloy and an inner sleeve formed out of a different material.

What is claimed is: 
     
         1 . A firearm comprising:
 a receiver operably coupled with a barrel; and   a forearm securable to the firearm and comprising a magnesium alloy body.   
     
     
         2 . The firearm of  claim 1  wherein the firearm is a modular rifle and wherein the receiver comprises an upper receiver and a lower receiver; the forearm and the barrel being mountable on the upper receiver and the lower receiver housing a trigger assembly. 
     
     
         3 . The firearm of  claim 1  wherein the magnesium alloy body has a layer of nickel plating applied thereto and a ceramic coating is applied over the layer of nickel plating. 
     
     
         4 . The firearm of  claim 1  wherein the magnesium alloy body forms an outer sleeve and the forearm further comprises an inner sleeve formed out of a non-magnesium material, the outer sleeve being disposed about and engaged with the inner sleeve. 
     
     
         5 . The firearm of  claim 4  wherein the inner sleeve comprises a steel material. 
     
     
         6 . The firearm of  claim 4  wherein the firearm is a modular rifle wherein the receiver comprises an upper receiver and a lower receiver; the lower receiver housing a trigger assembly and the forearm and the barrel are mountable on the upper receiver. 
     
     
         7 . The firearm of  claim 1  wherein the forearm is defined by a pair of separable parts which substantially encircle the barrel when secured together. 
     
     
         8 . The firearm of  claim 1  wherein the forearm is a unitary forearm which substantially encircles the barrel. 
     
     
         9 . A method of manufacturing a firearm forearm comprising:
 forming a magnesium alloy body; and   processing the magnesium alloy body to form at least a portion of the forearm.   
     
     
         10 . The method of  claim 9  further comprising the steps of plating the magnesium alloy body to form a layer of nickel plating on the magnesium alloy body and applying a ceramic coating on the layer of nickel plating. 
     
     
         11 . The method of  claim 9  wherein the step of forming a magnesium alloy body comprises thixotropically molding the magnesium alloy body. 
     
     
         12 . The method of  claim 11  wherein the magnesium alloy body has a surface roughness, R a , that is between approximately 35 microinches and approximately 60 microinches after molding and without any post-molding processing to smooth the surface. 
     
     
         13 . The method of  claim 9  wherein the step of forming a magnesium alloy body comprises extruding the magnesium alloy body. 
     
     
         14 . The method of  claim 13  wherein the magnesium alloy body forms a forearm that substantially encircles the barrel. 
     
     
         15 . The method of  claim 14  further comprising cutting the magnesium alloy body lengthwise to form two separable parts of the forearm. 
     
     
         16 . The method of  claim 15  wherein the two separable parts have the same configuration. 
     
     
         17 . The method of  claim 13  wherein the forearm includes an inner sleeve and an outer sleeve disposed about the inner sleeve and wherein the magnesium alloy body forms the outer sleeve of the forearm and the method further comprises providing a non-magnesium insert to form the inner sleeve. 
     
     
         18 . The method of  claim 9  wherein the forearm includes an inner sleeve and an outer sleeve disposed about the inner sleeve and wherein the magnesium alloy body forms the outer sleeve of the forearm and the method further comprises providing a non-magnesium insert to form the inner sleeve. 
     
     
         19 . The method of  claim 9  wherein the magnesium alloy body is formed out of an AZ91D magnesium alloy. 
     
     
         20 . The method of  claim 9  wherein the forearm has a configuration which adapts the forearm for use in a modular rifle having both a lower receiver housing a trigger assembly and an upper receiver securable to a barrel.