WO1996037747A1

WO1996037747A1 - A firearm locking system

Info

Publication number: WO1996037747A1
Application number: PCT/AU1996/000316
Authority: WO
Inventors: Bernard Christian Besselink
Original assignee: Bernard Christian Besselink
Priority date: 1995-05-26
Filing date: 1996-05-24
Publication date: 1996-11-28
Also published as: AUPN319495A0

Abstract

A self-loading firearm operating on the short-recoil principle which comprises a frame (1) having a handgrip (2) and adapted to receive a magazine. A breech block slide (3) is mounted for alternating longitudinal movement along the frame (1). A barrel (4) is provided which is able to move rearwards while positively locked with the slide member (3) by locking means (6 and 10). An actuating means (15 and 16) disengages the barrel (4) from the slide (3) after the high pressure period has passed. A cylinder (11) is located concentrically around the barrel (4) and communicates with the barrel bore (13) via passages (14). The action of propellant gases in the cylinder (11) retards the motion of the barrel (4) and slide (3) assembly allowing a lighter slide (3) to be used for a specific cartridge type.

Description

A Firearm Locking System

Technical Field

This invention relates to self-loading firearms and more particularly to self-loading pistols of the short-recoil- operated type.

Self-loading pistols receive the energy to operate their loading mechanism from the energy of recoil. The recoil force drives the slidable superstructure of the pistol rearward on a horizontal platform built into a lower frame to extract the spent cartridge case from the firing chamber and eject it from the pistol. The superstructure is then returned to the forward or battery position by a return spring and is adapted to strip the succeeding round from a magazine and insert it into the firing chamber. Subsequent shots may require discrete trigger operations in the case of semi-automatic pistols or the trigger to remain continuously depressed in the case of automatic pistols.

The self-loading pistols referred to above include pistols and machine pistols in contrast to other types of pistols which do not self-load such as revolvers.

Background Art

Self-loading pistols can be divided into a number of types such as pure blowback, delayed blowback, gas-operated, short-recoil-operated and long-recoil-operated.

With pure blowback pistols, the slidable superstructure consists only of a breech block slide. The slide is not locked to the barrel and the barrel is fixed to the frame. Immediately after firing, the recoil force starts to drive the slide rearwards thus commencing the extraction of the spent cartridge case. Thus, part of the extraction occurs during the high pressure period of the firing cycle. If the slide is too light, the case is extracted too soon and case rupture will result, leading to a failure of the loading cycle and possible injury to the user. As a result, the pure blowback type can only be used with low- powered cartridges since there is a practical limit to the mass of the slide. This type, however, is cheap to make and is quite common.

There are also a number of pure blowback pistols which use a gas retarding arrangement attached to the slide. The arrangement reduces the effect of residual gas pressure on the motion of the breech block slide and buffers the stop of the breech block slide.

Residual gas pressure is the gas pressure left in the barrel after the projectile has left the barrel. Residual gas pressure occurs due to the time it takes for the gas left in the barrel to leave via the muzzle. Although the residual gas pressure is low compared to the pressures when the projectile is moving in the barrel, it may persist for longer. The residual gas pressure can thus have a substantial influence on the recoil of the slide.

One such gas retarding arrangement consists of a piston attached to the slide and a cylinder attached to the frame. It should be noted that the stroke of the piston needs to be the same length as the travel of the slide. The cylinder is connected by a passage to the barrel bore. After firing, a small amount of propellant gas is bled into the cylinder. As the slide recoils, the piston attached compresses the bled propellant gas, thus producing a retarding force. It should be noted that the bullet has left the barrel by the time that this retarding process occurs, and so it should not be called a delayed blowback system as some do call it. A true delayed blowback process operates while the bullet is still in the barrel. As well, the initial case extraction still occurs during the high pressure period of the firing cycle.

With delayed blowback pistols, the slidable superstructure comprises a breech block slide but, as well, it has a delaying mechanism. The delaying mechanism is usually based on leverage in order to magnify the effective recoiling mass of the superstructure for a short period, thus reducing the extent of extraction of the spent cartridge case during the high pressure period of the firing cycle. This type can be used with more powerful cartridges but is quite expensive to make and is generally not cost competitive with the short-recoil-operated type.

With gas-operated pistols, the slidable superstructure comprises a breech block slide, and the pistol has a gas chamber and piston. The slide is locked to the barrel and the barrel is fixed to the frame. The gas chamber is connected by a passage to the barrel bore. After firing, the projectile travels along the barrel and passes the entrance to the passage and gas is bled into the chamber. The gas pressure drives the piston to actuate an unlocking mechanism after the high pressure period has passed. The slide is unlocked from the barrel after the bullet has left the barrel. The breech block slide starts its rearward motion and begins extraction of the spent cartridge case using the energy provided by the piston and the residual gas pressure in the barrel. After extraction, the spent cartridge case is ejected. The slide continues until full travel is reached. The cartridge case, therefore, does not move while the bullet is in the barrel. Since the case is not able to move relative to the barrel until the slide is disengaged from the barrel and the operation is not dependent on the mass of the slidable superstructure, this type is used for very powerful cartridges. However, this type is complex and costly and is not commonly used. With short-recoil-operated pistols, the slidable superstructure consists of a barrel and a breech block slide. Prior to the firing of the cartridge, the barrel is engaged to the breech block slide by a locking means. After firing, the recoil force drives both the slide and barrel rearwards, but since they are in engagement, the extraction of the case has not started. After the high pressure period has passed, an actuator begins to disengage the barrel from the slide. The barrel travels a short distance before coming to rest forward of the magazine, hence short-recoil, and is completely disengaged from the slide. The breech block slide continues and begins extraction of the spent cartridge case using its kinetic energy and the residual gas pressure in the barrel. After extraction, the spent cartridge case is ejected. The slide continues until full travel is reached. The cartridge case, therefore, does not move while the bullet is in the barrel. Since the case is not able to move relative to the barrel until the barrel is disengaged from the slide, this type is used for relatively powerful cartridges. However, revolvers are generally needed for the most powerful pistol cartridges; since again, there is a practical limit to the mass of the barrel and slide on short-recoil-operated pistols.

In short-recoil-operated pistols, the barrel may be locked to the breech block slide by a number of locking means. The barrel may be provided with peripheral ribs, studs, lugs or other means and may be rotated, cammed or otherwise engaged and disengaged from the slide.

Alternatively, a separate locking block may be used to lock the barrel to the slide.

Common methods include the tilting barrel method of locking and the falling block method of locking. Examples of the former are the US Model 1911A1 pistol and the FN

Browning 9mm High Power: examples of the latter are the Walther P38 and Beretta Model 92. In the tilting barrel method of locking, the muzzle end of the barrel is slidably and tiltably mounted at the forward end of the slide. The locking means comprises a number of transverse locking ribs located on the rear upper surface of the barrel and a number of mating locking slots on the slide member. Actuating means act to operate the locking means to disengage the barrel from the slide by urging the rear end of the barrel downwards.

In the falling block method of locking, the barrel is slidably mounted for straight line axial motion, and the locking means comprises a separate locking block provided with means for engaging the barrel to the slide. The actuating means comprises a cam on the frame operative to cam the locking block downwardly from engagement with the slide during initial rearward movement of the slide from the battery position and upwardly to engage the slide during final movement of the slide to the forward battery position.

Generally, the main components of a short-recoil-operated pistol are made of steel. A number of pistols use aluminium or polymer materials for the frame. However, the use of materials other than steel for the breech block slide is limited due to the lower density of these other materials. Because of practical size limitations, the use of lower density materials results in a slide of lower mass affecting the recoil behaviour of the pistol, when the same power cartridge is used.

A limitation in short-recoil-operated pistols of current design is the need for the barrel and slide mass to provide inertia. This factor controls the minimum mass of the arm in relation to the power of the ammunition used. In the past, the long recoil system was used for high powered pistols but this has been invalidated by experience. In long-recoil-operated pistols, the recoiling barrel and breech block slide are in engagement for a distance of about the length of a cartridge before disengagement is brought about. It is unnecessarily complicated for use in a weapon intended to be fired from one hand.

In contrast to the prior art pistols, it is the object of the present invention to provide a short-recoil-operated pistol with a lower mass recoiling superstructure relative to the power of the ammunition used than in conventional designs. It has previously been thought that self-loading short-recoil pistols were unsuitable for use with powerful ammunition. In the past, persons skilled in the art made use of gas-operation with self-loading pistols in order to use powerful cartridges.

Disclosure of Invention

Essentially a self-loading firearm of the short-recoil- operated pistol type according to the invention comprises a frame having a handgrip adapted to be grasped by the user and a receiver in the frame adapted to releasably receive a magazine. The magazine is adapted to be inserted into the receiver. A breech block slide member is slidably mounted for alternating longitudinal movement along the frame between a forward battery position and a rearward fully retracted position. The slide member carries a firing mechanism and is adapted to strip the succeeding round from the magazine.

A barrel is provided which is adapted to move rearwards along the frame while positively engaged by a locking means with the breech block slide member. The barrel has a piston means located concentrically about the axis of the barrel. After disengagement from the breech block slide member the rear end of the barrel comes to rest forward of the magazine.

The piston means is adapted at its inner diameter to provide a substantially gas-tight contact with the surface of the barrel and at its outer diameter to provide a sliding gas-tight seal with the surface of the cylindrical bore of the cylinder block means. One form of the piston means is an annular step formed in one piece with the barrel itself. Another form of the piston means is an annular piston ring separate from the barrel and held in place at its inner diameter by a groove formed in the barrel.

A locking means is provided which positively engages the barrel and the slide member during the high pressure period of the firing cycle. One form of locking means is of the rotating barrel locking type with locking ribs or interrupted thread locking. Another form of locking means is of the falling block type.

An actuating means acts to operate the locking means in order to disengage the barrel from the breech block slide member after the high pressure period has passed and to engage the barrel with the slide member on the return of the breech block slide member to the battery position. The form of the actuating means depends on the locking means used. With the rotating barrel, type, the actuating means may be a cam pin engaging a cam slot. With the falling block type, the actuating means may be a cam means on the frame operative to cam the locking block.

A cylinder block means which is fixed to the frame is provided with a cylindrical bore which is open at both ends and which at its rear end has a closure means located concentrically about the axis of the cylinder bore on the inside of the bore.

The closure means is adapted at its inner diameter to provide a sliding gas-tight seal with the surface of the barrel and at its outer diameter to provide a substantially gas-tight contact with the cylindrical bore of the cylinder block means. One form of the closure means is an annular step formed in one piece with the cylinder bore itself. Another form of closure means is an annular sealing ring separate from the cylinder bore and held in place at its outer diameter by a groove formed in the cylinder bore.

A variable volume chamber means is formed by the piston means, the surface of the barrel, the closure means of the cylinder bore and the cylindrical bore of the cylinder block means. The closure means is located to the rear of the piston means. The barrel is substantially in sliding contact with the closure means and the cylinder bore is substantially in sliding contact with the piston means.

The variable volume chamber means communicates with the barrel bore via passages located to the rear of the piston means such that propellant gases act to increase the pressure in the variable volume chamber means after the start of the motion of the projectile along the barrel bore. The resulting pressure increase in the variable volume chamber means provides a force to retard the motion of the barrel while engaged with the breech block slide member. A return spring urges the slide member to return to the battery position.

The barrel may be mounted in a number of ways. One way is to slidably mount the muzzle end of the barrel in the forward end of the breech block slide member and to slidably mount the rear end of the barrel in the cylinder block means. In another way, the front barrel mount may be fixed to the frame. A further way may be to slidably mount the rear end of the barrel in a separate mount fixed to the frame.

When the pistol according to the invention is fired, the projectile begins to move forward along the barrel bore and the recoil force starts to drive the barrel and breech block slide member rearward together. As the projectile moves further forward, it passes and uncovers the entrances to the passages. As a result, some of the propellant gases are able to pass into the variable volume chamber means. The pressure of the propellant gases in the variable volume chamber means provides a force to act against the cylinder block means and hence to the frame of the pistol and also provides an opposing force on the piston means. Since the piston means is fixed to the barrel and the barrel is locked to the breech block slide member, this action provides a force on the recoiling members opposite to the recoil force. The force from a return spring is also present. Thus, the motion of the recoiling barrel and slide is retarded. The rearward motion of the barrel acts to decrease the volume of the variable volume chamber means.

After the high pressure period has passed, the actuating means acts to operate the locking means in order to begin the disengagement of the barrel from the breech block slide member. The barrel continues until it reaches its rearmost position which is forward of the magazine and disengagement is complete. The variable volume chamber means is now at its lowest volume. The breech block slide member continues rearward but its motion is not influenced by the variable volume chamber means, since the barrel is now completely disengaged from the slide member. The slide member extracts the spent cartridge case and ejects it from the pistol. The breech block slide member continues until it reaches its rearward fully retracted position. The return spring is now in its most compressed state.

The compressed return spring urges the breech block slide member forward. As the breech block slide member reaches the magazine, the succeeding round is stripped from the magazine in the usual manner and inserted into the firing chamber. The face of the breech block slide contacts the breech opening of the firing chamber and the barrel is urged forward from its rearmost position. The barrel begins its engagement to the slide via the locking means and under the action of the actuating means. The loading cycle is completed on the return of the barrel and the slide member to the battery position. The volume of a variable volume chamber means is now at its maximum.

The number of passages to the variable volume chamber means depends on the profile of pressure increase required. Since there is initially a gas flow between the barrel bore and a variable volume chamber means, the length and cross-sectional area of the passages determines the rate of equilibration of pressure between the two.

The dimensions depend on the pressure profile required. A passage may be a circular hole, a longitudinal slot or other orifice.

Since some propellant gas is bled from the barrel bore and is not available for propelling the projectile, the muzzle velocity for a given cartridge type and barrel length is marginally reduced. The peak pressure in the barrel is also reduced if the passage is revealed before the peak pressure is reached. This would normally be the case. Since the stroke of a variable volume chamber means is related to the travel of the barrel and not of the slide, the volume of a variable volume chamber means is relatively small. It should be noted that the muzzle velocity to weight ratio for a pistol according to the invention is superior to that of a conventional self- loading pistol. The characteristics of a self-loading pistol according to the invention are such that the further the entrance to a passage is along the barrel bore, the higher the muzzle velocity, but the larger the effective cross-sectional area of a variable volume chamber means needs to become in order to maintain the same recoil behaviour.

As already mentioned, the prior art use of a gas cylinder retarding arrangement attached to the slide of blowback pistols has long been known. However, it has never been apparent to persons skilled in the art to utilise a concentric gas chamber around the barrel of a short-recoil pistol in order to reduce the mass of the slidable superstructure.

The advantage of the present invention with respect to gas-operated self-loading pistols is that the present invention provides a solution to the problem of using relatively powerful ammunition but is less complex in construction and relatively lighter.

The first preferred embodiment of the invention comprises a self-loading firearm of the short-recoil-operated pistol type in which the locking means is of the rotating barrel locking type. Typically in this embodiment, the forward end of the breech block slide member surrounds the barrel. The muzzle end of the barrel is slidably mounted in the front barrel mount located at the forward end of the slide. The locking means comprises a number of longitudinal locking ribs located on the barrel substantially in a radial semicircular arrangement and a matching number of locking ribs located on the inside of the slide member which are fully aligned and in abutting engagement when locked in the battery position. The actuating means acts to operate the locking means in order to disengage the barrel from the slide member while in rearward motion by rotating the barrel. The actuating means comprises a pin located on the underside of the barrel adapted to engage a slot formed in a block fixed to the frame. The slot has a longitudinally aligned section at its forward end and a helical section at its rear end. The helical section engages the pin to rotate the barrel to disengage the barrel from the slide. As a result, the barrel is movable in a straight line rearwards during the high pressure period of the firing cycle and thereafter the barrel is rotated in order to remove the barrel locking ribs from alignment with the matching locking ribs on the slide thus disengaging the barrel from the slide. On the return to the battery position, the actuating means reverses the process to engage the barrel with the slide via the locking means. It should be clear to a person skilled in the art that there are other combinations of conventional cams, cam slots and grooves which can be combined with other camming surfaces, pins and protuberances to produce the required rotation of the barrel as described above and not require a change to the novel features of the invention.

A second preferred embodiment of the invention comprises a self-loading firearm of the short-recoil-operated pistol type in which the locking means is of the falling block locking type. Typically in this embodiment, the forward end of the breech block slide member surrounds the barrel. The muzzle end of the barrel is slidably mounted in the front barrel mount located at the forward end of the frame. The locking means comprises a separate locking block connected to the barrel and accommodated substantially beneath the underside of the barrel. The locking block is provided with means for engaging the slide during the high pressure period of the firing cycle, thus locking the barrel and slide together. The actuating means comprises a cam means on the frame operative to cam the locking block downwardly from engagement with the slide during the initial rearward movement of the slide from the battery position and upwardly to engage the slide during final movement of the slide to the forward battery position.

It should be clear that the self-loading firearm according to the invention is provided with a locking system specifically to allow the use of a breech block slide of a lower mass than is conventionally used for a specific ammunition type. As a result, a self-loading pistol according to the invention using common pistol ammunition, such as 9mm Parabellum, is able to have a slide of a lower mass than normally used. Alternatively, it implies that a pistol according to the invention of similar dimensions and materials to those pistols currently used is able to use a more powerful cartridge. In the case of a slide of lower mass, materials of a lower density may be used. Low density materials include materials of a suitable strength and a specific gravity of less than 3.0, examples are polymers and composite polymers, die-cast metals and aluminium alloys. Examples of polymer materials are polyetherimide polymer or composite polymers having polymers combined with teflon, glass or graphite materials.

An advantage in using polymers or die-cast metals is that the processing of such materials by injection moulding is less costly than that of machining steel. Another advantage in being able to use polymer materials is that these materials are non-corrosive and self-lubricating. With some types of ammunition, the barrel and components of the variable volume chamber means may also be made of polymer materials or other low density materials.

The slide may also be of a composite construction having a subunit of the breech block slide member comprised of a breech block slide face with a forward extension adapted to engage the locking means constructed of a high strength material, such as steel. The rest of the slide is constructed of a low density material and carries the subunit.

The lightweight slide resulting from the current invention may be used with a lightweight frame made from a polymer material, aluminium or other low density materials as is used in a number of current pistol designs.

A further benefit of the current invention is that for pistols made of conventional materials such as steel, the net force on the breech block is less; and so, if used in automatic fire mode, the recoil behaviour of the pistol will be more controllable, having a reduced cyclic rate and a breech block slide with lower kinetic energy and momentum. This arrangement will also allow shorter barrel travel if desired.

The dimensioning of all components of a firearm according to the invention will depend on the materials used and would be clear to a person skilled in the art. As well, a firearm according to the invention may be designed to operate as a closed breech or open breech weapon. Although not all the alternative arrangements are shown or specifically described, all of them must be considered to be within the scope of the invention.

Brief Description of Drawings

The construction and operation of preferred embodiments of the subject invention will be more fully understood from a reading of the following detailed description as illustrated by the accompanying drawings. The embodiments shown in the drawings are only given by way of example and in no way limit the scope of the present invention. The drawings are described as follows:

Figure 1 represents a side elevation of a pistol according to the invention, with a longitudinal cross-sectional view of the forward part of the pistol, and with the breech block slide member in the battery position and hammer not cocked.

Figure 2 represents a side elevation of a pistol according to the invention, with a longitudinal cross-sectional view of the forward part of the pistol, and with the breech block slide member in the fully retracted position, the barrel fully rearward and the hammer cocked.

Figures 3 to 5 inclusive each represent a longitudinal cross-sectional view of the forward part of a pistol according to the invention and show the relationship between projectile position in the barrel bore and the position of various parts of the pistol.

Best Mode for Carrying Out the Invention

As shown in Figures 1 and 2, the illustrated self-loading firearm embodying the subject invention is of the short- recoil-operated pistol type using the rotating barrel method of locking with an actuating means consisting of a cam pin engaged with a cam slot. As such, the illustrated firearm has the overall configuration of a number of well- known pistols. The general features of magazine, and trigger, hammer and firing mechanism are well-known and readily apparent to persons skilled in the art and, therefore, will not be described in detail herein.

The self-loading firearm illustrated in Figures 1 and 2 comprises a frame 1 having a handgrip 2 including a receiver adapted to receive a magazine. A breech block slide member 3 mounted for alternating longitudinal movement along frame 1 surrounds the barrel 4 and has a front barrel mount 5 of a bush type at its forward end adapted to allow the muzzle end of the barrel 4 to slide through. The breech block slide member 3 has five slide locking ribs 6 arranged radially and located towards the forward end of the breech block slide member 3 on the inside of the breech block slide member 3. The breech block slide member 3 bears a firing device (not shown) . The lower forward end of the breech block slide member 3 is adapted to accept the forward end of the return spring guide rod 7 and is able to slide along the guide rod to compress the return spring 8.

The barrel 4 is borne in the front barrel mount 5 and the cylinder block means 9 so that the barrel 4 is able to move rearwards while positively locked with the slide member 3. The barrel 4 has five barrel locking ribs 10 arranged radially and located substantially midway along the barrel 4. The slide locking ribs 6 and the barrel locking ribs 10 comprise the locking means.

As shown in Figures 1 and 2, the subject invention differs to conventional pistols in that it has the novel feature of a variable volume chamber means comprising a cylinder 11 incorporated into the cylinder block means 9 and a piston means 12 formed on the barrel 4. The variable volume chamber means is able to communicate with the barrel bore 13 via passages 14. The piston means 12 and the narrower rear section of the barrel 4 carry the barrel 4 in the cylinder block means 9.

The actuating means comprises a cam pin 15 fixed to the underside of the barrel 4 and a cam slot 16 formed in a block 17 fixed to the frame 1. The cam slot 16 has a longitudinally aligned section at its forward end which allows the cam pin 15 to move rearwards without rotating the barrel 4 and a helical section at its rear end. The helical section engages the cam pin 15 to rotate the barrel 4 clockwise to disengage the barrel 4 from the breech block slide member 3 (as shown in Figure 2) .

As Figures 1 and 2 show, the subject invention is provided with a helical coil compression return spring 8 mounted below and axially parallel to the barrel 4.

It should be noted that the trigger mechanism is mounted rearwards of the magazine, as in many conventional pistol designs.

The general operation of the pistol allows the firing of a round and as the projectile begins to move forward, the recoil starts to drive the barrel 4 and breech block slide member 3 rearward. Figure 3 shows the cartridge case 20 and projectile 21 in the firing chamber 19 before firing, and the positional relationship between the projectile 21 and the passages 14. As the projectile 21 moves further forward, it passes and uncovers the entrances to the passages 14, as shown in Figure 4. Some of the propellant gases pass into the variable volume chamber means increasing the pressure and thus provide a force to oppose the recoil force and retard the motion of the recoiling barrel 4 and breech block slide member 3. As the barrel 4 moves rearwards, the piston means 12 moves into the cylinder 11 to decrease its volume. During the high pressure period, as shown in Figures 4 and 5, the barrel 4 slides rearwards in the front mount 5 and the cylinder 11. By the time the high pressure period has passed, the cam pin 15 has engaged the helical section of the cam slot 16 and the barrel 4 is being rotated clockwise as well as continuing rearwards. The clockwise rotation of the barrel 4 acts to disengage the barrel locking ribs 10 from the slide locking ribs 6. By the time the cam pin 15 has reached its rearmost position, the breech block slide member 3 has completely disengaged from the barrel 4. The barrel 4 has reached its rearmost position and the variable volume chamber means is at its lowest volume. The breech block slide member 3 continues rearward to extract the spent cartridge case and eject it from the pistol. The slide 3 continues until it cocks the hammer 18 and obtains its rearward fully retracted position where the return spring 8 is fully compressed. This final condition is shown in Figure 2.

The compressed return spring 8 urges the breech block slide member 3 forward. As the breech block slide member 3 reaches the magazine, the succeeding round is stripped from the magazine in the usual manner. The round is inserted into the firing chamber 19 while the barrel 4 is in its rearmost position. The face of the breech block slide member 3 contacts the breech opening of the firing chamber 19 and the barrel 4 is urged forward from its rearmost position. The barrel 4 is rotated anticlockwise as well as continuing forward because the cam pin 15 bears against the forward surface of the helical section of the cam slot 16. The anticlockwise rotation of the barrel 4 acts to align the barrel locking ribs 10 with the slide locking ribs 6. When the locking alignment is complete, the barrel 4 continues forward and the cam pin 15 travels along the longitudinally aligned section of the cam slot 16. The barrel 4 and breech block slide member 3 come to rest on hitting the stop provided by the cylinder block means 9. The barrel 4 and breech block slide member 3 have completed the operational cycle and returned to the battery position and the weapon is cocked and ready for firing. The volume of the variable volume chamber means is again at its maximum.

The invention is not intended to be limited to the specific form of the embodiment shown, which is presented for illustrative purposes only. Rather, it contemplates all of the variations and modifications coming within the scope of the claims.

Claims

1. A self-loading firearm of the short-recoil-operated pistol type comprising a frame having a handgrip adapted to be grasped by the user; a receiver in said frame adapted to releasably receive a magazine; a magazine adapted to be inserted into said receiver; a breech block slide member slidably mounted for alternating longitudinal movement along said frame between a forward battery position and a rearward fully retracted position where said slide member carries a firing mechanism and is adapted to strip the succeeding round from the said magazine; a barrel adapted to move rearwards along said frame while positively engaged by a locking means with said breech block slide member and where after disengagement from said breech block slide member the rear end of said barrel comes to rest forward of said magazine; a locking means which positively engages said barrel and said breech block slide member during the high pressure period of the firing cycle; an actuating means which acts to operate said locking means in order disengage said barrel from said breech block slide member after the high pressure period has passed and to engage said barrel with said breech block slide member on the return of the said breech block slide member to the battery position,- a cylinder block means fixed to the frame having a cylindrical bore which is open at both ends; a piston means located concentrically about the axis of said barrel and adapted at its inner diameter to provide a substantially gas-tight contact with the surface of said barrel and at its outer diameter to provide a sliding gas-tight seal with the surface of the cylindrical bore of said cylinder block means; a closure means at the rear end of said cylinder block means located concentrically about the axis of the cylinder bore on the inside of the said cylindrical bore and adapted at its inner diameter to provide a sliding gas-tight seal with the surface of said barrel and at its outer diameter to provide a substantially gas-tight contact with the cylindrical bore of said cylinder block means,- a variable volume chamber means formed by said piston means, the surface of said barrel, said closure means and the cylindrical bore of said cylinder block means where said closure means is located to the rear of said piston means and where said barrel is substantially in sliding contact with said closure means and the cylinder bore is substantially in sliding contact with said piston means and where said variable volume chamber means communicates with the barrel bore via passages located to the rear of said piston means such that propellant gases act to increase the pressure in said variable volume chamber means after the start of the motion of the projectile along the barrel bore and where the resulting pressure increase in said variable volume chamber means provides a force to retard the motion of said barrel while engaged with said breech block slide member; and a return spring which urges the said breech block slide member to return to the battery position.

2. A self-loading firearm according to Claim l of the rotating barrel locking type wherein said locking means comprises a number of longitudinal locking ribs located on said barrel substantially in a radial semicircular arrangement and a matching number of locking ribs located on the inside of said breech block slide member which are fully aligned and in abutting engagement when locked in the battery position; and said actuating means acts to operate said locking means in order to disengage said barrel from said breech block slide member while in rearward motion by rotating said barrel.

3. A self-loading firearm according to Claim 2 wherein said actuating means comprises a pin located on the underside of said barrel adapted to engage a slot formed in a block fixed to said frame where said slot has a longitudinally aligned section at its forward end and a helical section at its rear end which engages said pin to rotate said barrel to disengage said barrel from said breech block slide member.

4. A self-loading firearm according to Claim 1 of the falling block locking type wherein said locking means comprises a separate locking block connected to said barrel accommodated substantially beneath the underside of said barrel where said locking block is provided with means for engaging said breech block slide during the high pressure period of the firing cycle,- and said actuating means urges said locking block downwards from engagement with said slide during initial rearward movement of said breech block slide member from the battery position and upwards to engage said breech block slide member during final movement of said breech block slide member to the forward battery position.

5. A self-loading firearm according to Claim 1 wherein said breech block slide member is of a composite const-ruction having a subunit of said breech block slide member comprised of a breech block slide face with a forward extension adapted to engage said locking means constructed of a high strength material and where the rest of said breech block slide member is constructed of a low density material and carries the said subunit.

6. A self-loading firearm according to Claim 5 wherein said high strength material is steel and said low density materials include materials of a suitable strength and a specific gravity of less than 3.0.