Abstract:
The present invention is a modified bolt assembly and firing mechanism for creating a replica MG 34 Mauser rifle. The present invention provides for an MG 34 replica which fires from a closed bolt firing weapon, and is capable of only semi-automatic operation. The modified bolt assembly and firing mechanism of the present invention include design elements that deter conversion of the semi-automatic MG 34 Mauser rifle replica into a fully automatic weapon.

Description:
This application claims priority under 35 USC 119 (e) from provisional application No. 60/226,836 filed Aug. 22, 2000, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention is a modified bolt assembly for an MG  34  Mauser rifle in order to provide semi-automatic operation whereby a single cartridge is fired with each pull of the trigger. More specifically, the present invention allows for the creation of a replica MG  34  Mauser rifle which fires from a closed bolt, and is capable of only semi-automatic operation, while also inhibiting conversion of the firearm to fully automatic operation. 
     BACKGROUND OF THE INVENTION 
     There has been and continues to be an interest in collecting and shooting weapons that have been developed for, and used by the military. This interest is held by many civilians, particularly those who served in the military. Because many of these firearms are capable of fully automatic operation, private ownership is limited to qualified individuals who acquire a Class II or Class III firearms dealer&#39;s license, or those individuals who apply for and obtain the requisite permission from the local authorities where they reside, and the Bureau of Alcohol, Tobacco and Firearms “ATF” to become the registered owner of a fully automatic firearm. 
     Semi-automatic firearms, on the other hand, are not subject to such a rigorous procedure to own and fire legally, and can currently be legally transferred between individuals. However, while there is a good selection of handguns and rifles capable of semi-automatic operation, including some “civilian” versions of military firearms, original fully automatic military firearms are not readily available in semi-automatic versions. There are numerous reasons for this, including the cost of the original firearm, the cost to convert it, the necessity for a gunsmith to perform the conversion arid, most significantly, the diminishment of value of the fully automatic firearm by converting this firearm into semi-automatic operation. Not withstanding the foregoing reasons, there is a desire for original firearms that have been legally converted to semi-automatic operation and thus more easily acquired by civilians. 
     SUMMARY OF THE INVENTION 
     The present invention is a modified bolt assembly and firing mechanism for an MG  34  Mauser rifle, which allows a firearms enthusiast to create and/or own a semi-automatic MG  34  replica which fires from a closed bolt. Modifications are made to the bolt and the firing mechanism which includes the sear arm, the disconnector and the rocker. The bolt is modified to fire when it is locked with the barrel. The bolt includes a firing pin adapter which also works to make the weapon fire only semi-automatically. In addition to modifying the bolt and the firing mechanism, minor modifications are made to the receiver of the weapon in order to receive the modified bolt and firing mechanism components. Both the disconnector and the sear arm of the firing mechanism, include design elements that prevent the weapon from being readily converted back to fully automatic operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the modified bolt assembly for an MG  34  Mauser rifle will become apparent to those skilled in the art from the following detailed description of the invention in light of the accompanying drawings in which: 
     FIG. 1 is a side view of an MG  34  Mauser Rifle; 
     FIG. 2A is a side view of a first embodiment of the firing mechanism of the present invention; 
     FIG. 2B is a side view of a second embodiment of the firing mechanism of the present invention; 
     FIG. 3A is a side view of the sear arm of the firing mechanism of the present invention; 
     FIG. 3B is a top view of the sear arm of the firing mechanism of the present invention; 
     FIG. 4A is front view of the firing pin adapter of the firing mechanism of the present invention; 
     FIG. 4B is a side view of the firing pin adapter of the firing mechanism of the present invention; 
     FIG. 5A is a side view of the rocker of the firing mechanism of the present invention; 
     FIG. 5B is a top view of the rocker of the firing mechanism of the present invention; 
     FIG. 5C is a front view of the rocker of the firing mechanism of the present invention; 
     FIG. 6A is an assembled side view of the inertia firing pin assembly of the present invention; 
     FIG. 6B is a disassembled side view of the inertia firing pin assembly of the present invention; 
     FIG. 6C is a top view of the spacer of the inertia firing pin assembly of the present invention; 
     FIG. 6D is a side view of the spacer of the inertia firing pin assembly of the present invention; 
     FIG. 7A is an elevational view, in section, through the receiver looking rearwardly at the front end of the bolt as it is adapted to move through the receiver toward the barrel; 
     FIG. 7B is a top view of the receiver portion shown in FIG.  7 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     Shown in FIG. 2A is a first embodiment of the modified firing mechanism  14  of the present design. The mechanism  14  includes a bolt assembly  28  having locking lugs  30 , a bolt head  32 , and a bolt housing  34 . Placed within bolt housing  34  is the firing pin  56  including a face  58  for striking the primer of a cartridge (not shown), and a shaft  60 . Fixed about firing pin shaft  60  is the firing pin spring  54 . At the end of shaft  60  opposite firing pin face  58 , is attached the cocking nut  38 . A firing pin adapter  36  is affixed about firing pin shaft  60  adjacent cocking nut  38 . 
     Firing mechanism  14  further includes a modified sear arm  42  having a positive engagement cam  44  and a sear arm spring  46 . Within the pocket  45  of sear arm  42  is placed rocker  48  which is pivotally attached to the receiver (not shown) of firing mechanism  14 . Adjacent to rocker  48  is disconnector  40  which is pivotally attached by a pin to the trigger  50 . Adjacent trigger  50  is placed trigger spring  52 . 
     FIG. 2B illustrates another embodiment of the proposed modification. Many of the components of this embodiment are identical to that shown in FIG. 2A with the following alternate components. This embodiment includes an inertia firing pin  70  rather than a straight mechanical firing pin, as an added safety feature. It also includes an inertia firing pin sleeve  72  which is retained by non-removable sleeve retaining pin  76 . Inertia firing pin sleeve  72  acts as the firing pin spring support. A carbide bolt guide  78  is also fused into the inside of the receiver wall, with a matching groove  80  provided in the bolt assembly to prevent the use or introduction of an unmodified bolt assembly. Finally a spacer  74  is press-fit into the bolt assembly to prevent the use of a standard firing pin, as an added safety measure. The inertia firing pin assembly is also shown in FIGS. 6A through 6D. 
     Referring to FIGS. 3A and 3B, there is shown the sear arm  42  of the present invention, isolated from the firing mechanism. Front portion  65  of sear arm  42  engages with the firing pin adapter  36  (as shown in FIGS. 2A,  4 A and  4 B). Adjacent to front portion  65  is a detent  68 . When assembled, the front portion  41  of disconnector  40  extends upwardly through pocket  68  in sear arm  42 . This allows disconnector front portion  41  to engage firing pin adapter  36  upon firing of the rifle. Front portion  41  releases the firing pin shaft  60  and firing pin  56  upon the user pulling the trigger  50 . This is done by front portion  41  moving downwardly and no longer engaging firing pin adapter  36 . 
     The rear portion  66  of sear arm  42  forms a platform upon which sear arm spring  46  is placed. Above pocket  45  is a positive engagement cam  44 . Positive engagement cam  44  acts to lock firing pin  60  in the cocked position after a cartridge has been discharged, in case of failure of the sear spring  46  or the presence of dirt or corrosion within the firing mechanism. This further ensures that only one round of ammunition is discharged for each depression or pull of the trigger. In doing so, positive engagement cam  44  engages the firing pin adapter  36  of the bolt  28 . The positive engagement cam is an added device to ensure the return of the sear arm, in case of a spring failure or the presence of dirt within the receiver. 
     As can be seen in FIGS.  2 A and  5 A- 5 C, interconnecting sear arm  42  and disconnector  40  is the rocker  48 . Rocker  48  is pivotally attached within the trigger mechanism of the MG  34  replica rifle. Rocker  48  fits within pocket  45  of sear arm  42 . Upon depression of trigger  50 , the rear portion  43  of disconnector  40  engages rocker  48 , causing it to pivot and force the rear portion  66  of sear arm  42  upwardly and thus, front portion  65  downwardly. This releases the firing pin and allows firing pin face  58  to strike the primer of a cartridge (not shown), causing the cartridge to discharge. 
     In order to modify an MG  34  Mauser rifle to semi-automatic operation, an MG  34  rifle kit is first obtained from a gun dealer. Known dealers of these MG  34  Mauser rifle kits are Ohio Ordnance and Philadelphia Ordnance. In creating a semi-automatic MG  34  Mauser replica, the following modifications and alterations have been made to the receiver, obtainable from Philadelphia Ordnance in an unfinished state, the bolt and the firing mechanism. 
     Within the receiver, side grooves  82  or guides are milled out of each side of the receiver in order to cooperate with the rollers  84  on the bolt. These grooves  82  are milled to a narrower width than those in an original fully automatic MG  34  rifle. Adjacent to the grooves  82  are cams as are found in the original MG  34  Mauser rifle. Depending on the state of the receiver when purchased, the receiver may have to be bored out to allow for the original cams to be affixed to the receiver. 
     A narrow groove  86  is milled into the bottom of the receiver to ensure that only the modified bolt as described herein, and not the original fully automatic bolt, will fit within the receiver. This groove also prevents the full automatic trigger parts from being used and converting the MG  34  rifle back to fully automatic operation. 
     The bolt is modified to operate only in semi-automatic operation and to lock with the barrel during firing of the cartridge so as to fire from a closed bolt position. The roller extensions on the bolt head are shortened to engage the guides formed within the receiver to facilitate rotation of the bolt during operation. Shortening of the roller extensions on the bolt head also prevents use of the standard fully automatic MG  34  bolt assembly. 
     The engagement lug on the bottom of the bolt housing, on the original fully automatic bolt, is removed. A slot  80  approximately {fraction (3/16)} of an inch wide, and approximately one (1) inch long is milled into the bottom rear of the bolt housing  34  to allow the firing pin adapter  36  (as shown in FIG. 2A) to pass through the bolt housing  34 . 
     The sear assembly which includes the pin, the sear arm and the sear spring have also been removed from the bolt head and placed within the trigger mechanism of the present design. The sear cam surface of an original MG  34  bolt assembly is also removed from the bolt head. 
     As shown in FIG. 2A, the disconnector  40  has been re-shaped from the original MG  34  trigger disconnector. The reshaped disconnector  40  passes upward through the sear arm  42  in order to disconnect the trigger  50  when disconnector  40  is struck by the firing pin adapter  36 . The disconnector  40  is comprised of two pieces, a front portion  41  and a rear portion  43 . Front portion  41  selectively abuts rear portion  43  at a lap joint  39 . As trigger  50  is pulled or depressed by the user, the front portion  41  of disconnector  40  moves rearwardly, as it is pinned to the trigger  50 . This causes the front portion  41  to be lifted above rear portion  43 . With front portion  41  no longer abutting rear portion  43 , another round of ammunition cannot be discharged without resetting trigger  50  to its non-depressed position. Returning trigger  50  to its non-depressed position allows front portion  41  to abut against rear portion  43  at lap joint  39 . Thus, the disconnector  40  of the present design ensures that only a single round of ammunition is fired for each pull of the trigger. 
     In modifying the disconnector  40 , front portion  41  is milled out in order to clear the sear arm  42  of the firing mechanism. This allows for cooperation between the sear arm  42  and the disconnector  40 . Additionally, the rear portion of the original disconnector of an MG  34  rifle was cleared out to allow for operation of the rocker  48 . 
     Now referring to FIGS. 2A,  3 A and  3 B there is shown the sear arm of the firing mechanism of the present design. Sear arm  42  is provided with a positive engagement cam  44  which after firing of a cartridge interferes with the firing pin adapter  36 , so as to prevent another cartridge from being fired without resetting the trigger  50  to its non-depressed position. 
     The trigger housing assembly must also be modified in order to accommodate the modified sear arm  42  and rocker  48  of the present design. A pocket is created about the back of sear arm  42  in order to allow for the required sear arm spring  46 . At the front of the trigger housing assembly, a relief cut is made to allow for clearance of sear arm  42 . At the rear of the trigger housing assembly, a relief cut is made to clear rocker  48 . 
     In operation, the locking lugs  30  on the bolt  28  are locked with the cams formed on the inner surface of the barrel  16 . The user pulls backward on the handle (not shown) of the bolt  28 . After being pulled completely backward and released, bolt  28  slides through the receiver and a cartridge is removed from the cartridge belt and placed within the barrel  16 . As the bolt  28  slides forward toward the barrel  16 , the rollers on the bolt ride within the grooves formed within the front portion of the receiver, causing bolt  16  to rotate, and the locking lugs  30  to lock with the cams formed on the inner surface of the barrel  16 . 
     During the process of loading the cartridge into the barrel, the firing pin  56  is drawn into the cocked position by engagement of the sear arm  42  and the firing pin adapter  36 . The replica MG  34  semi-automatic rifle is then ready to be fired. The safety mechanism of the rifle may then be engaged or the rifle may be fired. To fire the rifle, the user depresses the trigger causing the disconnector  40  to engage the rocker  48  which engages the sear arm  42  which releases the firing pin  56  within the bolt  28 . The firing pin face  58  then extends through the aperture formed in the front of bolt  28 . Firing pin face  58  contacts the primer of the cartridge discharging the bullet out of the muzzle  20  of barrel  16 . 
     Discharging the cartridge forces barrel  16  and bolt  28 , which are in the locked position to move rearward toward the back of the receiver. The rollers on bolt head  32  contact the cams on the receiver causing the bolt  28  to be unlocked from the barrel  16 . After unlocking with bolt  28 , the barrel is forced forward into its normal position by a spring within the receiver. Bolt  28  continues rearwardly and contacts the ejector plate, which causes the discharged round to be ejected from the receiver. So long as there are cartridges remaining in the cartridge belt, bolt  28  will continue to cycle cartridges into barrel  16  for firing upon each depression or pull of the trigger. However, only one cartridge is fired for each pull of the trigger. 
     After being modified, the MG  34  Mauser rifle operable to fire caliber that is authentic to the rifle, the 8 millimeter Mauser cartridge. However, the MG  34  may be converted to 0.308 caliber by changing the barrel and the receiver tray that is configured for this caliber. The modified MG  34  Mauser rifle is fed cartridges via a belt. Belts of different lengths may be used to hold different numbers of cartridges. Optionally, the MG  34  may be outfitted with a canister which holds the belt, and is attached to the receiver. 
     Creating a World War II era MG  34  Mauser rifle which operates semi-automatically, allows for an economical means for a military firearms enthusiast to legally own and fire a firearm which was originally designed as a fully automatic firearm, without having obtain the authorization to own a fully automatic weapon. 
     Although the principles, preferred embodiments and preferred operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the preferred embodiments herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.