Locking lug insert for a firearm receiver

The present invention relates to a locking lug insert which is inserted into the locking lug recess of a bolt action receiver. The insert defines a central aperture aligned with an elongated chamber in the receiver and one or more cut-out portions opening into the central aperture, one cut-out aligned with each locking lug groove. The cut-out portions are equal in number to the number of locking lug grooves formed in the receiver. The cut-out portions are sized so as to accommodate the locking lugs of the bolt when the bolt is in its closed position. The insert is caused to rotate in the locking lug recess when the bolt rotates, due to the interengagement of the locking lugs, with the cut-out portions.

FIELD OF THE INVENTION 
The present invention relates to an insert rotatably mounted within a 
locking lug recess of a firearm receiver. 
BRIEF DESCRIPTION OF THE PRIOR ART 
Firearm bolt actions are well known in the art and typically comprise a 
receiver defining an elongated chamber and a bolt slidably received within 
the chamber. The bolt has one or more lugs radially extending therefrom 
adjacent one end, which lugs slidably engage one or more elongated locking 
lug grooves formed in the receiver. This allows the bolt to slide with 
respect to the receiver between an open position, wherein a cartridge may 
be inserted into the receiver, and a closed position wherein the bolt 
forces the cartridge into a firing chamber. In order to lock the bolt in 
the closed position, the receiver also defines an annular locking lug 
recess extending around the periphery of the elongated chamber and 
dimensioned so as to accommodate the locking lug when the bolt is in the 
closed position. This allows the bolt to be rotated through a given angle 
to thereby move the locking lug out of alignment with the locking lug 
groove formed in the receiver. When in this position, the engagement of 
the locking lug with the locking lug recess prevents any movement of the 
bolt with respect to the receiver, including posterior sliding movement 
along the operating plane of the bolt. 
The receiver and the bolt are machined to close tolerances, but clearances 
must be provided to permit the sliding and rotational movement of the bolt 
with respect to the receiver. Debris accumulating within the locking lug 
recess may render the proper locking of the bolt difficult, if not 
impossible. Also, the clearances between the bolt and the receiver and the 
former empty space around the bolt face may allow the rearward escape of 
gasses from a cartridge should the cartridge rupture during firing. 
While it is known to provide a gas shield or baffle on the bolt to the rear 
of the locking lugs, such a shield or baffle does not prevent the 
accumulation of debris in the locking recess and will not prevent jamming 
of the bolt due to the presence of such debris. 
SUMMARY OF THE INVENTION 
The present invention relates to a locking lug insert which is inserted 
into the locking lug recess of the receiver. The insert defines a central 
aperture aligned with the elongated chamber in the receiver and one or 
more cut-out portions opening into the central aperture, one cut-out 
aligned with each locking lug groove. The cut-out portions are equal in 
number to the number of locking lug grooves formed in the receiver. The 
cut-out portions are sized so as to accommodate the locking lugs of the 
bolt when the bolt is in any position. The insert is caused to rotate in 
the locking lug recess when the bolt rotates, due to the interengagement 
of the locking lugs, with the cut-out portions. 
The insert may be formed of a low-friction plastic, nylon or metal, or 
combinations of both, impregnated with Teflon or graphite material such 
that it will keep the locking lug recess free of any accumulated debris 
and will facilitate the rotation of the bolt with respect to the receiver. 
The insert will also prevent the backward escape of gasses due to a 
cartridge rupture and will also provide a dampening effect to barrel 
vibrations. The insert will also protect the tip of the bullet from any 
deformation as it is advancing through the receiver into the firing 
chamber. It also makes it unnecessary to use lubricant in the locking lug 
recess, which may freeze the bolt closed in sub-zero temperatures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 illustrates a bolt action 10 attached to rifle stock 12 and 
associated with known trigger mechanism 14 and barrel 16. As shown in more 
detail in FIGS. 2 and 7, bolt action 10 comprises a receiver 18 which 
defines a longitudinally extending, elongated chamber 20. Receiver 18 also 
defines a pair of longitudinally extending locking lug grooves 22 located 
on either side of, and opening into, chamber 20. Although the invention 
will be described in relation to a receiver having a pair of such locking 
lug grooves, it is to be understood that a receiver having more or less 
than two such grooves can be utilized without exceeding the scope of this 
invention. The outer wall of receiver 18 defines an opening 24 which 
communicates with the elongated chamber 20 to facilitate the insertion and 
removal of a cartridge into the chamber 20. 
Receiver 18 also defines an annular locking lug recess 26 which extends 
around the periphery, and opens into, elongated chamber 20. Locking lug 
recess 26 is located adjacent end 18A of the receiver which is connected 
to an end of barrel 16 via threads 28. 
Bolt 30 has elongated, cylindrical portion 32 extending into elongated 
chamber 20. Bolt 30 has a pair of radially extending locking lugs 34 
located adjacent end 32A. Although two oppositely extending locking lugs 
34 are utilized for illustrative purposes, it should be understood that 
the number of locking lugs will be equal to the number of elongated 
locking grooves formed in the receiver. The length of elongated bolt 
portion 32 is such that locking lugs 34 are aligned with the annular 
locking recess 26 when bolt 30 is in its closed position, as illustrated 
in FIGS. 1 and 2. When bolt 30 is in its closed position wherein locking 
lugs 34 are aligned with elongated locking grooves 22, bolt 30 may be 
moved in the direction of arrow 36 posteriorly with respect to receiver 
18, as shown in FIG. 2. Thus, by sliding bolt 30 to the left as seen in 
FIG. 2, to its opened position wherein end 32A is located to the left of 
opening 24, it is possible to insert a cartridge into a chamber 20 or to 
remove a spent cartridge therefrom. By sliding bolt 30 to the right, as 
seen in FIG. 2, to its closed position, a cartridge in chamber 20 is 
forced into a firing chamber (not shown). 
Actuating handle 38 extends radially from elongated portion 32 and provides 
the operator with means to open, close, lock and unlock the bolt 30. When 
bolt 30 is in its closed, but unlocked position, handle 38 is oriented 
generally in the position shown in FIG. 4. In this position, locking lugs 
34 are still in alignment with locking lug grooves 22. In order to lock 
the bolt in its closed position, handle 38 and elongated portion 32 are 
rotated in the downward direction of arrow 40 to the position shown in 
FIG. 3. This serves to rotate locking lugs 34 within annular recess 26, 
thereby moving them out of alignment with the locking lug grooves 22. This 
prevents any movement of the bolt 30, including posterior sliding movement 
of the bolt 30 with respect to receiver 18 in the direction of arrow 36. 
The locking lug insert according to the invention is illustrated in FIGS. 5 
and 6 and comprises an insert body 42 defining a central aperture 44 and a 
pair of oppositely disposed, locking lug cut-outs 46 which open into 
central aperture 44. The number and location of cut-outs 46 should 
correspond to the number and location of locking lugs and locking lug 
grooves. Cut-outs 46 are sized and shaped to conform to the size and shape 
of the elongated locking grooves 22 and have sufficient clearance to 
accept locking lugs 34 therein. Insert body 42 is mounted in annular 
locking lug recess 26 such that the insert may rotate therein. The 
cut-outs 46 are normally aligned with elongated locking lug grooves 22 
such that, when bolt 30 is moved into its closed position, locking lugs 34 
enter the cut-outs 46. When bolt 30 is rotated into its locked position, 
the interengagement of the lugs 34 with the cut-outs 46 causes insert body 
42 to rotate within an annular locking recess 26. 
The presence of the body 42 and its rotational movement within annular 
recess 26 keeps the recess free of any debris which may ordinarily 
accumulate over the period of usage of the firearm. This maintains the 
ease of operation of moving the bolt between its locked and unlocked 
positions. Additionally, the small clearance between the inner surface of 
body 42 and the end of bolt 30 prevents the rearward escape of gasses 
should a cartridge rupture during firing. 
The insert may be fabricated from various materials, such as a plastic or 
metal. It is envisioned that the insert will be fabricated from nylon, 
steel and nylon, carbamite, etc. 
The positioning of the insert adjacent the end of the firearm barrel will 
also provide an additional damping for barrel vibrations, and will protect 
the tip of the bullet from any deformation as it advances from the 
receiver into the barrel firing chamber. The insert also provides 
additional locking lug surface area in contact with the threaded end of 
the barrel. 
The foregoing is provided for illustrative purposes only and should not be 
construed as in any way limiting this invention, the scope of which is 
defined solely by the appended claims.