Patent Description:
Firearms with a multi-part receiver have been known for a long time. Examples include the types M4 / M16 / AR15 or H&K G3, and their derivatives. In these firearms, the upper receiver part is connected to the lower receiver part by means of pins which run normal to the central plane of the firearm. The upper receiver part and the lower receiver part are inserted into each other during assembly; corresponding holes are provided in both parts, such that a front pin (also known as a pivot pin) and a rear pin (also known as a takedown pin) can be inserted, thereby producing the receiver connection.

By removing the rear pin, the upper receiver part can be opened about the axis of the front pin - hence the term "pivot pin. " In the open state, the breech is accessible and the firearm can be cleaned without completely disassembling it. To completely disassemble the firearm, the front pin must also be removed. <CIT> and <CIT> disclose special embodiments of pins for such firearms, making the handling easier and reducing the migration of water and/or debris into the detent track and/or the firearm, but the pin has still to be removed.

Modifications are known, for example, from <CIT>, where a hinge is provided instead of the pivot pin and the fixation takes place by means of a rotatable cam. Although the opening is simplified as a result, and the risk of loss is eliminated, a complete disassembly is extremely cumbersome. This, by way of example, practically prevents changing the barrel - necessarily with the upper in which it is mounted - in the field.

<CIT> discloses the use of a type of pseudojoint as a pivot pin, and a connecting device made of elastomer material at the rear end of the firearm. This soft connection cannot cope with the harsh operating conditions in the field; in practice this design does not occur.

As simple as the first arrangement may appear at first glance, it has its disadvantages: Despite various countermeasures, (both) pins are easy to lose, and significant forces - and in particular, shocks - are transmitted between the two receiver parts via the pins, such that these and the bearings are heavily loaded. Since the pins also substantially align the two parts relative to each other, all geometric changes to the pins are extremely negative due to the high load.

It is therefore the aim of the invention to create a mechanically solid connection, which can also be easily disassembled, between the upper receiver part and the lower receiver part, in particular with only one pivot pin.

According to the invention, these objectives are achieved by the features specified in claim <NUM> - in other words, in that a connecting mechanism is formed which comprises at least one pivot pin, a receiver pivot pin hole, and a connector element, and which works together with projections or recesses of the upper receiver part or lower receiver part of complementary shape. In the simplest case, the receiver pivot pin hole corresponds to a bore and can be formed on the upper receiver part (upper) and/or the lower receiver part (lower), and has an axis that is normal to the weapon median plane. The connector element has at least one hole and one slotted hole, the axes of which are normal to the weapon median plane. The pivot pin is designed to work together with the receiver pivot pin hole and the connector element, the pivot pin reaching at least through the lower (and/or upper) and at least through the slotted hole and the hole, wherein the slotted hole has its longitudinal extension, in the closed state, parallel to the barrel axis. Regions of complementary shape, namely at least one protrusion and/or one recess, are formed on the upper and the lower in such a way that they are in contact with each other (and prevent movement between the upper and lower in the weapon median plane, and normal to the barrel axis) when the pin is situated in an end region of the slotted hole, and in such a way that they are spaced from each other (and allow a movement between the upper and the lower in the weapon median plane, and normal to the barrel axis) when the pin is situated in the other end region of the slotted hole.

The listed components, such as the receiver pivot pin hole, connector element, protrusion and recess can, depending on requirements, be arranged by a person skilled in the art on the upper receiver part and/or the lower receiver part in order to work together in the manner according to the invention.

This enables the upper to be pivoted during assembly about the single pin, which is inserted in the slotted hole of the upper but not in its bore, until it rests on the lower; and then, possibly guided by guides, it is pushed in the direction of the barrel until the two complementary regions are in contact with each other. Then the pin located in the other end region of the slotted hole can also be pushed through (into) the bore of the upper; a stable connection is created by the combined action of the pin and the regions of complementary shape.

Practically the only condition that the regions of complementary shape must meet is that their geometry in the direction of the barrel axis is designed so that, in the closed state: parts of the upper have a greater distance axially from the axis of the pivot pin than regions of the lower, and so that these parts of the upper are "below" the regions of the lower. Generally speaking, this can be described as "sticking" a projection of the upper into a recess of the lower in the direction of the barrel axis.

In this way, a mechanically very strong connection is established; the regions of complementary shape, due to their dimensions, can do more for the alignment, as well as for force or torque transmission, than the two pins known in the prior art. The pin itself can advantageously, similarly to the prior art, be provided with pull-out locks, etc., but this is no longer the core of the invention.

As in the prior art, it does not matter which further parts the upper contains besides the barrel and the firing mechanism, and it does not matter which further parts the lower contains besides the trigger mechanism, and therefore these are not explained in more detail here.

Further components of the firearm, the invention is also suitable for pistols, in particular so-called "modularly constructed" pistols, but is explained below with reference to a carbine, such as the grip, the barrel, various safeties, the magazine well, or the magazine feed or shaft are likewise not explained in more detail here, since these do not concern the core of the invention, and a person skilled in the art, with knowledge of the invention, can simply make modifications based on his special technical knowledge, if necessary or desired at all.

Since the invention can be used not only with newly built and/or newly designed firearms, but can also be implemented by retrofit kits or conversion kits, the invention also and generally comprises a multi-part connecting mechanism which comprises the pivot pin, the receiver pivot pin hole with its axis normal to the weapon median plane, a connector element with the hole and the slotted hole with axes normal to the weapon median plane, the protrusion running in the direction of the barrel axis and the recess which is complementary in shape and function. These elements can be fitted in a suitable manner on the upper and the lower, but they can also be designed to be entirely or partially integral with the upper / lower.

The invention is explained in more detail in the following with reference to the drawings, in which:.

The terms left, right, up, down, front and back in the following always refer to the firearm from the point of view of the firearm when it is held ready to fire. The firearm has a weapon median plane going through the barrel axis and oriented vertically, which substantially forms a plane of symmetry; the barrel has a barrel axis that is referenced in the following for further orientation.

In the description and the claims, the terms "front," "rear," "above," "below" and so on are used in the generally accepted form and with reference to the object in its usual use position. This means that, for the firearm, the mouth of the barrel is "at the front," that the breech is moved "rearward" by the explosive gas, etc. Transverse to a direction substantially means a direction which is rotated by <NUM>° thereto.

<FIG> schematically illustrates a firearm having a barrel <NUM>, grip <NUM>, magazine <NUM>, stock <NUM>, handguard <NUM> and receiver <NUM>, which comprises the upper receiver part <NUM> and the lower receiver part <NUM>, and shows the barrel axis <NUM> with a dashed line.

<FIG> and <FIG> show exemplary exploded views of an embodiment of the invention. In <FIG>, the arrangement of the components for assembly is indicated with dashed lines. The connection for the receiver <NUM> comprises the upper receiver part <NUM> and the lower receiver part <NUM>, connector element <NUM> with hole <NUM> (initially and variously also referred to below as a bore) and slotted hole <NUM>, pivot pin <NUM>, and receiver pivot pin hole <NUM>, as well as a protrusion <NUM> and recess <NUM>, which are designed to be complementary to each other in shape and function.

In the embodiment shown, the protrusion <NUM> has a rear stop surface <NUM> on the end section <NUM> and is attached to the upper receiver part <NUM>. The recess <NUM>, which is complementary in shape and function, on the receiver end section <NUM> has a receiver counter surface <NUM> and, in the design shown, is formed on the lower receiver part <NUM>. In the closed state (when the firearm is ready for use), the protrusion <NUM> lies in the recess <NUM>, and the rear stop surface <NUM> lies directly on the receiver counter surface <NUM>. A rearward power transmission from the upper receiver part <NUM> to the lower receiver part <NUM>, as occurs, for example, when a shot is fired, takes place on the one hand via the rear stop surface <NUM> and the receiver counter surface <NUM>, and on the other hand via the pivot pin <NUM>, the connector element <NUM>, and the receiver pivot pin hole <NUM>.

The protrusion <NUM> and the recess <NUM> can be designed in numerous shapes that deviate from the illustration shown, for example cylindrical, stepped, toothed shapes, etc. In equivalent embodiments, the protrusion <NUM> can also be formed on the lower receiver part <NUM>, and the recess <NUM> can be formed on the upper receiver part <NUM>.

The connector element <NUM> is mounted in the upper or formed in one piece (integrally) with it; it has a hole <NUM> - cut out of a section called the "stud" <NUM>, which in the assembled state runs substantially parallel to the weapon median plane <NUM> (shown as a dashed line in <FIG>) - with an axis normal to the weapon median plane <NUM>, and has - on a section which in the assembled state also runs substantially parallel to the weapon median plane <NUM>, called the "lug" <NUM> - a slotted hole <NUM>, the longitudinal extension of which, in the assembled state, runs parallel to the barrel axis <NUM>. The rotary-sliding movement of the two parts relative to each other is made possible together with the receiver pivot pin hole <NUM> in the lower and the pivot pin <NUM>.

In the embodiment shown, the handguard <NUM> is shown with a lock <NUM>. On its front end (in the longitudinal direction), the handguard <NUM> completely surrounds the barrel; on the rear end, it is cut out at the top and has guide rails <NUM> on both sides, which are complementary in shape to the grooves <NUM> formed on both sides of the upper receiver part <NUM>. To connect the handguard <NUM> to the upper receiver part <NUM>, the handguard <NUM> and the upper receiver part <NUM> are inserted into each other in such a way that the grooves <NUM> receive the guide rails <NUM>, until a front stop surface <NUM> strikes a mating surface <NUM> of the handguard <NUM>. Due to the interaction of the guide rails <NUM> and the grooves <NUM>, the handguard <NUM> is secured to the upper receiver part <NUM> against unwanted movement transverse to the barrel axis <NUM>, and is secured against unwanted movement in the direction of the barrel axis <NUM> on the one hand by the interaction between the front stop surface <NUM> and the mating surface <NUM>, and on the other hand by the lock <NUM> together with the pivot pin <NUM> (see Fig. 8c and d).

In other embodiments, one or more stop surfaces, also with other shapes, can be formed - for example, step-shaped, surfaces with interruptions, etc..

Furthermore, instead of a handguard <NUM>, other add-on parts such as a grenade launcher can also be secured by means of a lock <NUM>.

<FIG> and <FIG> also show an abutment <NUM> which is fastened in the lower <NUM> with a retaining pin <NUM> and which forms the actual guides for the pivot pin <NUM> in the lower; it is explained in detail with reference to <FIG>.

In the simplest embodiment, the pivot pin <NUM> can be a smooth, cylindrical, and in particular circular-cylindrical round pin; in the embodiment shown, the pivot pin <NUM> is designed having a head <NUM> and body <NUM> and a three-part cam <NUM> and detents <NUM> on the body <NUM> (<FIG>).

<FIG>-d each show a detail of the receiver <NUM> with the upper receiver part <NUM> and the lower receiver part <NUM>, in a lateral plan view. <FIG> shows the receiver <NUM> in the closed state (closed position). <FIG> shows the receiver <NUM> in the unlocked state (unlocked position). The protrusion <NUM> is pushed completely out of the recess <NUM> in the running direction, and the end section <NUM> is thus spatially separated from the receiver end section <NUM>. <FIG> shows the receiver in the broken state (tilted position). In the embodiment shown, the upper receiver part is tilted out of the lower receiver part about the pivot pin, which acts as the axis of rotation (here without reference number). The end section <NUM> is tilted upwards away from the receiver end section <NUM>. In this position, the breech can be removed without having to completely dismantle the firearm, and cleaning is also easy. <FIG> shows the receiver <NUM> in the completely disassembled state, as it can be reached after removing the pivot pin: The upper receiver part <NUM> is completely separated from the lower receiver part <NUM> (separated position). <FIG> show the cross-sections of the receiver in the positions according to <FIG>, each in the section plane "Vn":.

<FIG> shows the closed position. The upper receiver part <NUM> and the lower receiver part <NUM> lie one inside the other, the upper and lower guiding surfaces <NUM> and <NUM> lie against other. The pivot pin <NUM> is situated completely inside the receiver <NUM> and protrudes through the receiver pivot pin hole <NUM>, the hole <NUM> formed on the stud <NUM> of the locking element <NUM> (clearly visible in <FIG>), the slotted hole <NUM> formed on the lug <NUM> of the connector element <NUM> (see also Fig. 9b or <FIG>), and the abutment pivot pin hole <NUM> (a hole, so-identified for differentiation) of the abutment <NUM>. The pivot pin <NUM> has a cam <NUM> with detents, and is held in position by means of a spring-loaded plunger <NUM>, <NUM>, as will be explained below. The stud <NUM> lies axially in the plane of the pivot pin <NUM>.

<FIG> shows the unlocked position. The pivot pin <NUM> is partially pulled out of the receiver <NUM> along its longitudinal axis, and releases part of the receiver pivot pin hole <NUM>, part of the abutment pivot pin hole <NUM>, and also the hollow <NUM> and the hole <NUM>. The movement of the pivot pin <NUM> is limited by the cam <NUM>. In the unlocked position, the upper receiver part <NUM> and the lower receiver part <NUM> are displaced relative to each other parallel to the barrel axis <NUM>, as compared to the closed position. The movement along the barrel axis <NUM> is limited by the interaction of the pivot pin <NUM> with the slotted hole <NUM>. Tilting about the pivot pin <NUM> is not yet possible. This unlocking movement can be illustrated by comparing <FIG> and <FIG>. From this comparison, it can be deduced that the stud <NUM> visible in <FIG> (with hole <NUM> through which the locking pin <NUM> extends), in the unlocked position in <FIG>, is no longer in the plane of the pivot pin <NUM>, and accordingly can no longer be seen in <FIG>. When the unlocking movement has been fully executed and the pivot pin <NUM> comes to stop in the second end <NUM> (<FIG>) of the slotted hole <NUM>, a tilting about the axis of the pivot pin <NUM> is possible.

The tilted position is shown in <FIG>; this position is reached by rotating (pivoting) the upper receiver part <NUM> relative to the lower receiver part <NUM>, with the longitudinal axis of the pivot pin <NUM> acting as the axis of rotation.

<FIG> shows the separated position; the upper receiver part <NUM> and the lower receiver part <NUM> are now completely separated from each other and no longer connected to each other. The pivot pin <NUM> is pulled out of the receiver <NUM> to the maximum extent along the third part of the cam, but is secured by a spring-loaded plunger <NUM>, <NUM> engaging in a detent <NUM> (<FIG>), to prevent it from falling out. In this position, the pivot pin <NUM> releases the lug <NUM> and the slot <NUM> (<FIG>) and no longer protrudes into the slotted hole <NUM>. Therefore, the upper receiver part can be completely separated from the lower receiver part.

<FIG>-d show longitudinal sections of the receiver in the weapon median plane <NUM>, in the positions according to <FIG>, the lower receiver part being partially cut out for better illustration. The movement of the upper receiver part <NUM> with the slotted hole <NUM> relative to the lower receiver part <NUM> by the span <NUM> (see also <FIG>) can be seen. In <FIG>, the closed position, the pivot pin <NUM> lies in the first (front, toward the muzzle) end <NUM> (<FIG> of the slotted hole <NUM>. In <FIG>, the unlocked position, the upper receiver part is moved by the span <NUM> (<FIG>) relative to the lower receiver part in the direction of the barrel. The pivot pin is in the second (rear, facing away from the muzzle) end <NUM> (<FIG>) of the slotted hole <NUM>. <FIG> shows the tilted position. The upper receiver part <NUM> is tilted relative to the lower receiver part <NUM>; the longitudinal axis of the pivot pin <NUM> represents the axis of rotation, and the position of the pivot pin <NUM> is freely movable within the slotted hole <NUM>.

For the sake of completeness, the separated state is shown in the same longitudinal section in <FIG>.

In <FIG>, the slotted hole <NUM> of the connector element <NUM> is shown in a detailed view. The slotted hole <NUM> is an elongated bore with a semicircular first end <NUM> and a semicircular second end <NUM>, and has a width (diameter) <NUM> that corresponds to the diameter of the first and second ends <NUM> and <NUM>, and also at least substantially to the diameter of the receiver pivot pin hole <NUM> and to the diameter of the hole <NUM>. The span <NUM> of the slotted hole <NUM> corresponds to the distance between the two center points of the two semicircles of the first and second ends <NUM> and <NUM>, and must be at least as large (greater in practice) as the length <NUM> of the axial overlap <NUM> of the two receiver parts (<FIG>), so as to - on the one hand - reliably enable their contact (in the closed position) and - on the other hand - to ensure their disengagement (in the unlocked position). In practice, in the closed position, the pivot pin <NUM> should have "air" in front of the end position in order to reliably leave the axial contact between the two receiver parts to the stop surface <NUM> and the counter surface <NUM>, and the two receiver parts should come free during axial displacement, at least right before the pivot pin reaches the other end position in the slotted hole, in order to reliably compensate for tolerances, thermal expansion, wear, etc..

<FIG> shows the protrusion <NUM> on the upper receiver part <NUM> and the protrusion length <NUM>. In order to allow a complete sliding out from the recess <NUM>, and to allow the tilting into the tilted state, the protrusion length <NUM> of the protrusion <NUM> is less than the span <NUM> of the slotted hole <NUM>. Preferably, the protrusion length <NUM> corresponds to <NUM> to <NUM> times the span <NUM>.

<FIG> and b show a preferred development of the pivot pin <NUM>, with the head <NUM> and body <NUM>, as well as with the cam <NUM> with detents <NUM>, wherein the pivot pin <NUM> is shown rotated by <NUM>° in <FIG>. As illustrated, the cam <NUM> can be designed with three sections, i.e., in three parts, with two parts parallel to the pin axis and one part running in the circumferential direction, which merge into each other and are thus connected to each other. In the configuration shown, the cam has three radially recessed detents <NUM> - for the closed, unlocked and separated positions.

In simple designs, the pivot pin can also be designed as a bare pin (circular cylindrical, without head and cam); other shapes with, for example a linear cam with or without detent and with or without loss protection, are also possible. In cooperation with the plunger, the cam can have a clearly defined stop point during the opening and closing. However, in addition, it can also be made flat so that it rotates automatically when the pivot pin is pressed. Designs with different cams for moving the pivot pin <NUM> in and out can also be contemplated.

The detent <NUM> cooperates with the spring-loaded plunger <NUM> and <NUM> shown in <FIG>, which is arranged in the abutment <NUM> in the embodiment shown, and thus allows the pivot pin <NUM> to be held in the closed, unlocked and separated positions and to fix it in a releasable manner. In the separated position, this also has a loss-preventing effect; the pivot pin <NUM> remains connected with the receiver <NUM>. The plunger <NUM> with the spring <NUM> can, for example and as shown in <FIG>, be attached in the abutment <NUM>. But it is also possible to attach the plunger <NUM> and spring <NUM> at another suitable location, for example in the receiver.

<FIG> also shows the abutment <NUM> located in the lower receiver part <NUM>, which in the multi-part embodiment shown is fixed in the receiver by means of the retaining pin <NUM> and abutment retaining pin holes <NUM>, <NUM> (<FIG>). The abutment can also be formed integrally on the lower receiver part (or upper receiver part). The slot <NUM>, which is at least substantially parallel to the weapon median plane <NUM>, forms a guide for the lug <NUM> provided on the connector element <NUM> in the exemplary embodiment shown (see also <FIG>) with the slotted hole <NUM>. The interaction of the lug <NUM> and the slot <NUM> when the upper receiver part and lower receiver part move relative to each other results in a guided and jam-free movement. In addition, the upper receiver part <NUM> and the lower receiver part <NUM> can be guided by their vertical overlaps on the sides with correspondingly designed upper and lower guiding surfaces <NUM> and <NUM>.

The depth and the cross-section of the cam <NUM> and the depth and shape of the detents <NUM> are such that there is no unintentional movement of the pivot pin <NUM> due to the action of the spring <NUM> on the plunger <NUM>. Rather, intentional and desired pulling (or during assembly: also pressing) makes removal possible without tools. Since the end face of the head is preferably aligned with the outside of the firearm, pressure must first be exerted on the opposite end face during dismantling, for example with the head of a cartridge, then the head <NUM> can be grasped and moved at the transition to the body <NUM>.

<FIG> shows the lock <NUM> in detail. On the mounting area <NUM>, the lock <NUM> is connected to the handguard <NUM> (<FIG>), for example by means of screws (not shown). In the closed (assembled) state, the molded hook <NUM> protrudes into the hollow <NUM> in the central region of the abutment <NUM> (<FIG>) in such a way that the notch <NUM>, with an inner diameter substantially corresponding to the slot width <NUM> (<FIG>), is concentric to the receiver pivot pin hole <NUM> (in the lower, <FIG>) and the abutment pivot pin hole <NUM> (in the abutment, <FIG>). The handguard <NUM> is thus held in position in the closed state by the interaction of the hook <NUM> on the lock <NUM> with the pivot pin <NUM>, and an undesired movement of the handguard in the direction of the muzzle is prevented.

The lock <NUM> can be connected to the handguard <NUM> in a fixed manner or a manner allowing disassembly, for example by means of rivets, screws, gluing, welding, etc., or can also be formed integrally on the handguard <NUM>. The hook <NUM> can be designed with the shape of a hook or with a functionally identical shaping, with a corresponding inner diameter, for example as an eyelet, sleeve, etc..

A preferred embodiment of the connector element <NUM>, with a hole <NUM> and a slotted hole <NUM>, is shown in <FIG>. It comprises the already-described lug <NUM> on which the slotted hole <NUM> is formed, and the stud <NUM> with the hole <NUM>. <FIG> shows a side view, and <FIG> shows a longitudinal section along the slotted hole median plane (dashed line in <FIG>).

Other embodiments of the connector element, with the hole <NUM> and the slotted hole <NUM>, are also possible. As a further example, a variant worked from the solid piece is shown in longitudinal section in <FIG>, wherein the hollow <NUM> used to accommodate the lock <NUM> is dispensed with in this variant.

It is clear to the person skilled in the art after what has been said and shown that the slotted hole (or the connector element <NUM>) does not have to be provided in the upper, but can instead be formed in the lower, which then also has a hole matching the longitudinal extension of the slotted hole; the pin is then (apart from rotation and axial displacement) fixedly arranged in the upper and executes the longitudinal movement with it.

Briefly, the invention relates to a firearm having a weapon median plane <NUM>, an upper receiver part <NUM> with a barrel <NUM> with a barrel axis <NUM>, and a lower receiver part <NUM>, which are detachably connected to each other, the connection comprising at least one pivot pin <NUM>, around the axis of which, normal to the weapon median plane, the two receiver parts <NUM>, <NUM> can pivot relative to each other between a closed position, which occurs in the ready-to-fire state, and an open position, and is characterized in that.

In the case of a "retrofit," the invention relates to the ensemble of the abutment <NUM>, connector element <NUM> and pivot pin <NUM> for suitable installation in a firearm - be it a pistol or carbine. Whether the installation is done by screwing, riveting, gluing, or in some other way is a question that a person skilled in the art can easily decide with knowledge of the invention and the firearm to be converted.

The invention is not limited to the illustrated and described exemplary embodiments, but can be modified and configured in various ways. In particular, the shown cross-sectional shapes of the mentioned receiver parts, pins, rails, recesses, etc. can be adapted to the given basic data; the lengths and the positions with respect to the receiver can also be easily adapted by a person skilled in the art with knowledge of the invention. In particular, equivalent designs are obvious with knowledge of the invention and can be carried out without further ado by a person skilled in the art.

Thus, instead of the connector element <NUM>, the holes <NUM>, <NUM> provided there can be provided directly in the upper / lower. Regardless of this, the abutment <NUM> can have a different shape or it can be dispensed with, and the receiver pivot pin hole <NUM> in the lower / upper then takes on the role of guide without the abutment pivot pin hole(s) <NUM>.

It should also be noted that in the description and the claims, terms such as the "lower region" of an object, refer to the lower half and in particular the lower quarter of the overall height; "lowermost region" refers to the lowermost quarter and in particular an even smaller part, while "central region" refers to the central third of the overall height. For the terms "width" and/or "length," this applies mutatis mutandis. All these terms have their generally accepted meaning, applied to the intended position of the object under consideration.

In the description and the claims, "substantially" means a deviation of up to <NUM>% of the stated value, if physically possible, both downward and upward, otherwise only in the appropriate direction; in the case of degrees (angle and temperature), and for indications such as "parallel" or "normal," this means ± <NUM>°. For terms such as "substantially constant" etc., what is meant is the technical possibility of deviation which the person skilled in the art proceeds from, and not the mathematical one. For example, a "substantially L-shaped cross-section" comprises two elongated surfaces, which merge at one end into the end of the other surface, and whose longitudinal extensions are arranged at an angle of <NUM>° to <NUM>° to each other.

All given quantities and percentages, in particular those relating to the limitation of the invention, insofar as they do not relate to specific examples, are understood to have a tolerance of ± <NUM>%; accordingly, for example: <NUM>% means <NUM>% to <NUM>%. With terms such as "a solvent," the word "a" is not to be considered to represent a singular numeral, but rather is to be considered an indefinite article or pronoun, unless the context indicates otherwise.

The term: "combination" and/or "combinations," unless otherwise stated, mean all types of combinations, starting from two of the relevant components up to a plurality or all of such components; the term "containing" also means "consisting of.

Claim 1:
A firearm having a weapon median plane (<NUM>), an upper receiver part (<NUM>) with a barrel (<NUM>) with a barrel axis (<NUM>), and a lower receiver part (<NUM>), which are detachably connected to each other by means of a connecting mechanism which comprises at least one pivot pin (<NUM>), about the axis of which, running normal to the weapon median plane (<NUM>), the two receiver parts (<NUM>, <NUM>) are pivotable, between a closed position in the ready-to-fire state and an open position, wherein the connecting mechanism comprises:
- the pivot pin (<NUM>),
- a receiver pivot pin hole (<NUM>) which passes through the upper receiver part (<NUM>) and/or lower receiver part (<NUM>) normal to the weapon median plane with an axis normal to the weapon median plane (<NUM>),
- a connector element (<NUM>) with at least one hole (<NUM>) and one slotted hole (<NUM>) with axes normal to the weapon median plane (<NUM>),
- a protrusion (<NUM>) formed on the upper receiver part (<NUM>) or lower receiver part (<NUM>) in the direction of the barrel axis (<NUM>), and a recess (<NUM>) on the upper receiver part (<NUM>) or lower receiver part (<NUM>) that is complementary in shape and function, wherein in the closed position, the pivot pin (<NUM>) protrudes through at least the receiver pivot pin hole (<NUM>) in one of the two receiver parts (<NUM>, <NUM>) and through the hole (<NUM>) and the slotted hole (<NUM>) of the connector element (<NUM>) in the other of the two receiver parts (<NUM>, <NUM>).