GB2189581A - Blank firing attachment - Google Patents

Abstract

The design of some guns does not allow a blank firing attachment to be fitted axially onto the end of the gun barrel. In order to overcome this problem, particularly in relation to a machine gun, we provide a body 1 having a radial opening 5 which allows for fitting radially. Also provided is a shoulder 7 which engages an abutment 27 of the gun and clamping means in the form of a spindle 15 screw threaded into the body 1 and engagable with the end of the gun barrel 29. The spindle 15 has a through bore 31 which allows release of gas pressure whilst creating a desired predetermined lock pressure. <IMAGE>

Description

SPECIFICATION Blank firing attachment The present invention relates to a blank firing attachment for a gun and in particular for a machine gun to simulate with blank rounds the cartridge ejection and/or loading which occurs when live rounds are used.

When an automatic gun, such as a machine gun fired using live ammunition, a back pressure is created which is used to eject the spent cartridge and to load the next cartridge.

This enables continuous firing be achieved when the trigger is held without repeated operation for each round. When blanks are being fired, the gas pressure from the cartridge is insufficient to achieve cartridge ejection and this has to be done manually. Thus, only one round can be shot at a time.

By fitting a blank firing attachment to the end of the barrel the gas flow from the,barrel is restricted so that a back pressure is produced which simulates that generated with a live round, so that cartridge ejection is achieved and accordingly, continuous firing is possible.

A wide variety of blank firing attachments are known and they are fitted onto the barrel of the gun by various means according to the design of the gun. Where the end of the barrel is threaded internally a blank firing attachment can be fitted to those threads and where the end of the barrel projects from the body of the gun and is provided with the sighting lug, the blank firing attachment can be fitted onto the end of the barrel and provided with a catch to locate with the lug. All the known designs have to be fitted axially onto the end of the gun barrel.

None of the above mentioned blank firing attachments are suitable for use with a machine gun without a projecting barrel or which is not threaded at the end or in which the construction of the gun is such that axial fitting of a blank firing attachment onto the end of the barrel is not possible. One such gun where the known designs of blank firing attachment are unsuitable is the MP5K produced by Heckler and Kock GmbH.

It is an aim of the present invention to provide a blank firing attachment which is suitable for fitting to a machine gun in which the construction of the gun is such that the blank firing attachment cannot be fitted axially onto the end of the gun barrel. It is a particular aim of the present invention to provide a blank firing attachment for the above mentioned MP5K, the short barrelled version of the MP5.

According to the present invention then, there is provided a blank firing attachment for a machine gun, comprising a body having a radial opening therein for fitting about a gun barrel, which fitting is done radially, a shoulder at one end of the body for abutment with a part of the gun or barrel, and clamping means movable relative to the body and engageable with the gun to locate the body in position about the end portion of the barrel and means for restricting gas flow from the barrel.

Conveniently, the means for restricting gas flow comprises a through hole/bore in communication with the gun barrel. More especially the through bore is in a spindle threaded into the body so as to be axially movable therein and preferably substantially in alignment with the axis of the gun barrel. The bore is preferably smaller than the gun bore and dimensioned to give the desired back pressure. It may be of one diameter or of stepped diameter. More preferably, the spindle is engageable with the end of the gun barrel so that the spindle also serves as the clamping means. Conveniently the spindle carries a boss which is received in a bore in the body and an end face of this boss is adapted to engage the end of the gun barrel. Alternatively, separate clamping screws may be threaded into the body and arranged for engagement with the gun, say the end of the barrel.

It is also preferred that the spindle has a cylindrical extension which projects into the barrel of the gun. This serves as both a location/centring means for the blank firing attachment, but also has the added advantage of serving to increase the back pressure generated. This allows a larger through bore to be used than would otherwise be possible without the extension.

It is further preferred to have a knurled coliar at the end of the spindle which is accessible outside the body to facilitate turning of the spindle to move it between a withdrawn position, for fitting of the blank firing attachment to the gun, and a fitted position. It is also convenient to provide a threaded locking collar on the spindle to lock it in the clamped position.

The present invention will now be further described further hereinafter, by way of example only, with reference to the accompany drawings; in which: Figure 1 is a plan view of the blank firing attachment according to the present invention; Figure 2 is a section on line Il-I I of Figure 1; Figure 3 is an end view of the blank firing attachment of Figure 1; Figure 4 is a sectional view of the blank firing attachment in its position of use showing the end part of the gun barrel; Figure 5 is a side view of an alternative embodiment; and Figure 6 is an end view of the embodiment of Figure 5.

Referring firstly to the drawings of Figures 1 to 4 there is illustrated a blank firing attachment comprising a body 1 having a hollow cylindrical portion 3 provided with a radial opening thereto 5. At one end of the hollow cylindrical portion is a shoulder 7 in the form of a flange also having a radial opening thereto 9. The body also has a threaded bore 11 at the end remote from the shoulder which opens into larger diameter bore 13 coaxial with the bore 11 and leading into the hollow cylindrical portion 3 with which it is also coaxial.

Received threadingly in the bore 11 is a spindle 15 which has an enlarged boss 17 dimensioned to be received movably in the bore 13. The end of the spindle outwardly of the body has securely attached thereto a knurled collar 19. This is attached after a knurled locking collar 21 is threaded onto the spindle.

After fitting of the knurled collar the spindle cannot be removed from the body, just moved axially. Extending from the boss 17 in the illustration is a cylindrical member 23 whose external diameter is dimensioned to fit into the bore of the gun barrel to which the blank firing attachment is to be fitted. It is preferably a clearance fit therein so that it will not touch the rifling inside the barrel and therefore no damage can result. Cylindrical member 23 may also be sleeved with copper, and the boss 17 is the only thing that touches the very end of the barrel but from many tests, we know that no damage or wear is possible. A copper washer 25 or the like is fitted onto the member 23 and secured to the boss 17.

The spindle has a through bore 31 which serves as a restrictor for the flow of gases from the gun barrel when a blank is fired. The length of the extension and the diameter/area of the through bore in the spindle are such that the desired back pressure is produced to cause ejection of the spent cartridge. It has been found that by providing the extension into the bore of the barrel a larger diameter of through bore can be used in the spindle. This simplifies manufacturing as long small diameter bores are difficult to machine.

To fit the blank firing attachment about the end of the gun barrel, the spindle 15 is turned to withdraw the boss 17 and the cylindrical extension thereof 23 into the bore 13 so that it does not project into the hollow cylindrical portion 3 and thereby does not interfere with fitting of the body of the blank firing attachment onto the gun barrel. This is done by sliding the body radially relative to the gun barrel axis. The gun barrel of the Heckler and Kock GmbH MP5K, with which the illustrated blank firing attachment is to be used, has adjacent the end of the barrel 29 a locating boss 27. This boss 27 is received in the hollow cylindrical portion 3 whilst the shoulder 7 is arranged to fit around the barrel and abut against the boss 27 as will become apparent hereafter.

With the body in the position described, the spindle 15 is turned by way of the knurled collar 19 so that it moves axially within the body, by virtue of the threaded engagement therewith. Thus, the boss 17 and extension thereof move axially, to the left in the illustration. The extension is thus positioned within the bore. of the gun barrel. The boss 17 is screwed into contact with the end of the gun barrel. This pulls the shoulder 7 into abutment with the locating boss 27 of the gun thereby holding the blank firing attachment in position whilst at the same time forming a seal at the end of the barrel. The spindle is locked in position by tightening the locking collar 21 against the end of the body 1. This prevents the threaded spindle working loose in use.

Thus, it will be seen that by designing the blank firing attachment to be fitted into position radially, it can be used for guns where the barrels do not project axially from the body or barrel locaters or for other guns of a construction where axial fitting is not readily possible.

Alternative embodiments are envisaged, for example, the body may be provided with one or more grub screws which pass through threaded holes therein and into engagement with the barrel, say at the end face thereof. In such an arrangement the boss of the spindle may be dispensed with and the knurled collar screwed up tight to the end of the body. Alternatively, the locking collar may be employed.

It is the convention and regulation in certain countries for blank firing attachments to be coloured yellow. In order to avoid the colouring wearing off where it is a painted finish, it is proposed to provide ribbing on the conical section of the body say either circumferential or longitudinal so that the colour cannot wear within the troughs of the ribs even if the ridges wear.

Referring now to figures 5 and 6 there is shown a modified embodiment of blank firing attachment. The basic construction corresponds to that described above and like reference numerals have been used to denote like parts. The following differences will be noted: Firstly, the knurled collar 19 attached to the spindle 15 is of larger diameter for convenience of gripping as is the diameter of the locking collar 21. Indeed I find it convenient to have these correspond substantially to the diameter of the body 1.

Secondly, instead of tapering the body, I provide a plurality of circumferential ribs 35 spaced apart. These serve advantageousiy as cooling fins by increasing the surface area and can also receive the regulation yellow colouring. Six fins are shown in the illustration although this is not to be taken as limiting.

Indeed I find seven to be particularly effective in practice.

Thirdly, I provide a spring washer 37 which is interposed between the body 1 and the locking collar 21. The spring washer prevents the locking collar working loose when the locking collar is lightened up to the body.

I also disperse with the copper washer 25 and now have the end of the boss 17 engage directly on the end of the gun barrel.

I also find it advantageous to have the through bore 31 of stepped diameter, initially starting large and then reducing to a smaller size. An initial taper 37 is advantageous. The length and diameter of the respective parts is chosen to give sufficient back pressure to eject the spent blank cartridge and to load the next cartridge.

In making the blank firing attachment the spindle 15 is threaded into position from the left hand end in the illustration and then the spring washer, locking collar fitted on before the knurled collar which is fixed onto the end of the spindle.

Fitting of the blank firing attachment of figures 5 and 6 onto the gun follows the proceedure described with reference to figures 1 to 4.

Claims (11)

1. A blank firing attachment for a machine gun, comprising a body having a radial opening therein for fitting about a gun barrel, which fitting is done radially, a shoulder at one end of the body for abutment with a part of the gun or barrel and clamping means movable relative to the body and engageable with the gun to locate the body in position about the end portion of the barrel and means for restricting gas flow from the barrel.

2. A blank firing attachment as claimed in claim 1 in which the means for restricting gas flow comprises a through bore of or associated with the body.

3. A blank firing attachment as claimed in claim 1 in which an extension surrounding an inner end of the through bore in use extends into the end of the gun barrel.

4. A blank firing attachment as claimed in claim 2 or 3 in whcih the through bore is of stepped diameter.

5. A blank firing attachment as claimed in any one of claims 2, 3 or 4 in which the through bore is in a spindle which is threaded into the body so as to be axially movable therein and in substantial aiignment with the gun barrel.

6. A blank firing attachment as claimed in claim 5 in which the spindle is engageable with the end of the gun barrel.

7. A blank firing attachment as claimed in claim 5 or 6 in which the spindle carries a knurled collar to facilitate turning of the spindle to move it between a withdrawn position for fitting of the blank firing attachment to the gun, and a fitted position.

8. A blank fixing attachment as claimed in claim 5, 6 or 7 in which a locking collar is threaded into the spindle and engageable directly or indirectly with the body .o lock the spindle in place.

9. A blank fixing attachment as claimed in claim 8 in which a spring washer is interposed between the locking collar and the body.

10. A blank fixing attachment as claimed in a preceeding claim in which clamping screws are threaded into the body, say axially, and arranged for engagement with the gun, say the end of the barrel.

11. A blank fixing attachment constructed and arranged substantially as hereinafter described with reference to and as illustrated in the accompanying drawings of figures 1 to 4 or 5 and 6.