NZ611493B - An Improved Adjustable Muzzle brake for a Rifle - Google Patents

Abstract

611493 A muzzle brake has an inner generally cylindrical portion attachable to a gun barrel, typically by screwing on, and an outer sleeve rotatable relative to the inner portion so that either holes on the sleeve and inner portion are aligned for muzzle brake effect or are non-aligned to provide no muzzle brake effect. o muzzle brake effect.

Description

AN IMPROVED ADJUSTABLE MUZZLE BRAKE FOR A RIFLE.

Cross-reference to related application(s).

This application is a continuation, and claims the benefit, of N.Z. Provisional Patent Application No. 600475, filed 06 June 2012.

Technical field of the invention The present invention relates to muzzle brakes for firearms, and more particularly to an adjustable muzzle brake for a sporting or military firearm that reduces recoil forces.

Background of the invention When a high-powered rifle is fired, the gas that propels the projectile out of the end of the rifle’s barrel accumulates behind the projectile and upon discharge from the firearm creates a recoil force of the firearm back towards the shooter, largely due to the ‘jetting effect’ of that propellant gas as it is released to atmosphere. This force is proportional to the mass and type of propellant and its operating pressure, and is inversely proportional to the mass of the weapon.

Another recoil force associated with the discharge of a firearm relates to the inertia effect of the bullet/projectile being fired down the barrel/bore of said firearm, and this is directly proportional to the projectiles given mass and velocity as it travels through the barrel.

However, because the time taken for the bullet to travel from the breech end of the barrel to the muzzle is relatively short, particularly in pistols or small arms, the recoil action due to the above factors is, to the shooter, essentially one. This combined recoil force can be quite severe, especially in high powered rifles used for long-range hunting, target, or tactical shooting applications, and may result in pain, discomfort and fatigue to the shooter. It also puts considerable stress upon the component parts of the firearm, and can also cause the shooter to lose sight of the target being aimed at. To reduce these side effects, “muzzle brakes” are often used to lessen this recoil force back towards the shooter.

Many and diverse muzzle brakes have been developed over the years. Some try to compensate for muzzle rise, as well as reducing recoil force, and also some claim to create less noise or shockwave effect to the shooter, compared with other muzzle brake designs.

Examples of prior art muzzle brakes are shown in Figures 19 to 22 and are shown mounted to a firearm in Figure 1. A conventional muzzle brake design consists of a cylindrical body and a bore hole. The gas ports/vents and gas expansion chambers are formed by the standard method of drilling round holes at an angle exactly 90 degrees (or perpendicular) to the centreline central axis of the body/bore, and the area between those chambers/vents forms the effective baffle wall ahead of the next gas expansion chamber.

Such a brake design has been shown in tests to provide a recoil reduction of about 60% with standard factory-loaded ammunition, when tested with such ‘magnum calibres’ such as 7mm Rem. Mag., and .300 Win Mag. However, the measured recoil reduction drops to about 45% when tested with more efficient cartridges such as 7mm-08 Rem or .308Win.

Most muzzle brakes comprise an attachment placed on the muzzle end of a firearm (Figure 1) (either by a threaded joint, or a clamping arrangement) which reduces recoil by dissipating propellant gasses radially from the direction of the barrel/bore of the firearm through a series of openings within that attachment. In deflecting the gas away from the end of the barrel (often at right-angles to it), some of the gas impinges on the opening surfaces (or ‘baffles’) inside the muzzle brake, and is reflected to the sides and/or back towards the shooter. The reaction to the change of direction of the escaping gases exerts a forward pulling force on the muzzle brake and, in turn, the firearm. This reduces the rearward-directed force component which causes the recoil. In effect, the muzzle brake harnesses the main cause of recoil and converts it into a partial cure, resulting in greater barrel stability, improved accuracy, and less recoil travel of the firearm.

Thus, firearms equipped with conventional muzzle brakes often sound much louder to the shooter than the same firearms with no muzzle brake. The re-direction of the propellant gas also creates a shock-wave effect which can be extremely damaging to human hearing, and as such it is well known advice that firearms equipped with muzzle brakes should never be fired without firstly ensuring that the shooter (and others nearby) are wearing adequate hearing protection. With the huge range of modern hearing protectors available now, from compact foam or moulded rubber earplugs to grade 5+ earmuffs, this is no longer a major issue as it may have been in the past.

Firearm users often use these hearing protectors while discharging a muzzle brake- equipped rifle at a shooting/practice range only to later remove the muzzle brake for actual hunting in the field where the hunter and his companions may not have such hearing protectors. This practice actually negates any accuracy and recoil-reducing advantage achieved by using the muzzle brake. The weight of the muzzle brake itself mounted on the end of the barrel will alter the mass and harmonic/vibration profile of the barrel. Consequently, muzzle brake fitting or removal may cause a significant deviation in barrel performance upon aiming and discharge. Therefore, a firearm sighted-in with a muzzle brake installed may prove to be reasonably accurate, however the same firearm may not be fired as accurately when the muzzle brake has been removed, and there will almost always be some difference in bullet point-of-impact ‘grouping’ on the target with the muzzle brake either fitted or removed.

It is therefore a primary object of the present invention to provide a muzzle brake which may be functionally engaged or disengaged as may be desired without the necessity for removal of the muzzle brake from the firearm, and to reduce as much recoil as possible when engaged without being overly large in size.

The above and other objects of the invention will in part be obvious and will be hereinafter more fully pointed out in connection with the detailed description of the accompanying drawings.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

Accordingly, it is an object of the present invention to provide a new and improved muzzle brake for projectile type weapons which, overcomes the above short-comings, removes or compensates for as much recoil effect as possible for its’ given length/size, or to at least provide the public with a useful choice.

Brief description of the invention The present invention may be said to broadly consist in an adjustable muzzle brake, adapted for connection to the muzzle of a firearm, for a projectile to pass through, in the preferred form comprising or including: A rigid cylindrical shaped tube/body including, a rearward end for connection to said barrel muzzle. This tube/body presents a plurality of openings (or vents) extending transversely through its’ sidewall, at least three expansion chambers along and in communication with a centrally located borehole. Each said expansion chamber is separated by a baffle about said borehole, and each said expansion chamber is in communication with at least four vents on an outward surface of said cylindrical tube/body. A cylindrical sleeve is disposed concentrically around the tube/body. This sleeve also has a plurality of openings (or vents) extending through its’ sidewalls. The openings presented by the sleeve are alignable to the openings presented by the tube/body. The sleeve and tube/body are joined by a means allowing one to rotate with respect to the other. This permits the muzzle brake to be placed in an engaged condition wherein the openings of the sleeve are aligned with the openings of the tube. This joining means also allows the muzzle brake to be functionally disengaged wherein the openings in the sleeve are not aligned with the openings in the tube/body.

A locking mechanism retains the outer sleeve into place on the cylindrical tube body, while also maintaining correct rotational alignment to ensure that the braking function remains either fully engaged, or fully disengaged.

Preferably said expansion chambers increase in size down said muzzle brake from said muzzle to an exit of said borehole distal from said muzzle.

Preferably said gas openings/vents also increase in size in proportion to said increasing gas expansion chambers.

Preferably the final baffle wall section at the forward/exit end of the brake should be greater in thickness than any other baffle wall in said muzzle brake.

Preferably said bore hole has a diameter that is 0.020” – 0.030” larger than a largest diameter of a bullet to be fired through the barrel of that particular firearm which the muzzle brake is attached to.

Preferably said vents are at an angle of between + 5 to 10 degrees to a plane orthogonal to a major axis of said borehole.

Preferably said vents are at an angle of between - 5 to 10 degrees to a plane orthogonal to a major axis of said borehole.

Preferably said vents are at an angle back towards said muzzle such that the exhausting gasses from behind said projectile when fired are jetted back towards said muzzle which acts to pull the firearm forward slightly.

Preferably said vents are offset in such a way that exhausting gasses from behind said projectile when fired, ‘jet’ to create a torque on said muzzle brake that tightens or retains said muzzle brake onto said firearm barrel, if that muzzle brake is attached via conventional right-hand threading.

When the muzzle brake is functionally engaged, most of the gases produced when the firearm is discharged escape laterally through the openings/vents presented by the device. This lateral and slightly rearward flow of discharge gases significantly reduces both recoil effect and muzzle jump.

When the muzzle brake is functionally disengaged, the gases produced by the discharge of the firearm escape through the front/exit end of the muzzle brake behind the projectile.

The disengaged muzzle brake does, surprisingly, actually still provide a slight amount of recoil reduction and braking effect on the firearm. When disengaged, the muzzle brake remains rigidly affixed to the end of the barrel of the firearm, thereby preserving the length, mass and vibration profile of the firearms barrel, and thus maintains the same bullet point-of-impact on the test target as when the brake is fully engaged.

In this preferred form of the invention when the muzzle brake is functionally engaged, the energy of the propellant gases are conserved and exploited by distributing the vented gases amongst the expansion chambers, such that the reaction surfaces in each gas expansion stage experience substantial forward thrust forces. It is preferable that the reaction surfaces in each stage experience approximately equal thrust forces. It is important that substantially all of the gases not be vented through the first one or two stages, but instead be vented nearly equally through all of the stages. Each stage thereby provides a part of the overall counter-recoil force, and the total counter-recoil force increases markedly. To do this, it is necessary that the brake restrain and conserve the exploding gases by sizing the vent apertures and the expansion plenums with respect to their adjacent apertures or plenums, or by a combination thereof. Thus, successive expansion chambers and vents increase in volume towards the muzzle (forward) end of the brake. In practice this is required due to the pressure dropping relatively in each successive expansion chamber stage, such that in order for a similar volume of gas to be vented in a given time, then the chamber/vent area must also increase proportionally.

Further, due to the dropping pressure levels, the final baffle wall must be of greater thickness than any other baffle in the muzzle brake, in order to increase the ‘dwell time’ as the bullet passes through it, thereby forcing as much as possible of the remaining lower pressure gases to exit out to the sides through the adjacent vent/openings, thus reducing the amount of gas rushing out of the front/exit borehole.

As used herein the term “and/or” means “and” or “or”, or both.

As used herein “(s)” following a noun means the plural and/or singular forms of the noun.

The term “comprising” as used in this specification means “consisting at least in part of”.

When interpreting statements in this specification which include that term, the features, prefaced by that term in each statement, all need to be present, but other features can also be present. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner.

It is intended that reference to a range of numbers disclosed herein (for example, 1 to 10) also incorporates reference to all rational numbers within that range (for example, 1, 1.1, 2, 3, 3.9, 4, 5, 6, 6.5, 7, 8, 9 and 10) and also any range of rational numbers within that range (for example, 2 to 8, 1.5 to 5.5 and 3.1 to 4.7).

The entire disclosures of all applications, patents and publications, cited above and below, if any, are hereby incorporated by reference.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements and features, and where specific integers are mentioned herein which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

Other aspects of the invention may become apparent from the following description which is given by way of example only and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred forms of the present invention will now be described with reference to the accompanying drawings in which; Figure 1 Shows an example of a prior art rifle with muzzle brake fitted at the end of the barrel, Figure 2 Shows a side elevation of an adjustable muzzle brake according to the present invention, shown also is a side view of a threaded rifle barrel to which the invented muzzle brake is attached, Figure 3 is a sectional side elevation of the muzzle brake in Figure 2 along line AA of Figure 4, Figure 4 is a front end elevation of muzzle brake shown in Figure 2 and Figure 3, Figure 5 Shows a perspective view from the upper left front of an adjustable muzzle brake according to the present invention, shown also is a perspective view of a threaded rifle barrel to which the invented muzzle brake is attached, Figure 6 Shows a quarter-sectioned perspective view of the muzzle brake shown in Figure 2-16 viewed from the upper left front, Figure 7 Shows a perspective view of the muzzle brake shown in Figure 2-16 viewed from the upper left rear, Figure 8 Shows a perspective view of the muzzle brake shown in Figure 2-16 viewed from the upper left rear, Figure 9 is a sectional side elevation of the muzzle brake in Figure 2 and Figure 3 including sectional view of the barrel to which it is fitted, Figure 10 Plan view of the muzzle brake shown in Figure 2-16, Figure 11 Left side elevation of the muzzle brake shown in Figure 2-16, Figure 12 Underside view of the muzzle brake shown in Figure 2-16, Figure 13 Front end elevation of the muzzle brake shown in Figure 2-16, Figure 14 Rear end elevation of the muzzle brake shown in Figure 2-16, Figure 15 Perspective view from the upper left front of the muzzle brake shown in Figure 2-16, with gas port venting function open (on), Figure 16 Perspective view from the upper left front of the muzzle brake shown in Figure 2-16, with gas port venting function closed (off), Figure 17 Shows a perspective view from the upper left front of an adjustable muzzle brake according to the present invention which incorporates a quick-change mechanism with a knurled threaded end-cap, shown with gas ports venting function open (on), Figure 18 Shows a perspective view from the upper left front of the muzzle brake shown in Figure 17, with the gas ports venting function closed (off), Figure 19 Illustrates the left side elevation of a prior art radial-ported muzzle brake, Figure 20 Illustrates a perspective view from the upper left front of a prior art radial-ported muzzle brake, Figure 21 Illustrates a perspective view from the upper left rear of a prior art radial-ported muzzle brake, and Figure 22 Illustrates a perspective 3D view from the left front of a prior art radial-ported muzzle brake.

Detailed description of the invention Preferred embodiments will now be described with reference to Figures 1 through 18.

The present invention is an adjustable muzzle brake 6a 6b for reducing the recoil effect associated with discharging a firearm 15 while minimising the added effective length to the barrel of the firearm 15. The muzzle brake 6a 6b is applied to the end of a barrel of a firearm 15, and in addition directs the expelled propellant gas charge to the sides and back toward the muzzle of the firearm 15 to provide a forward force to counteract recoil forces of the firearm during firing.

As shown in Figures 2 through Figure 18 of the preferred forms the adjustable muzzle brake 6a 6b is made up of a cylindrical shaped body 17 having a rear end 16 adapted for the attachment to the muzzle 4 of the firearm 15. The adjustable muzzle brake has a cylindrical body 17, and telescoped over body 17 is an elongated rigid tubular sleeve 18 extending from the front end 23 to approximately 79-83% down the length of body 17 along a generally longitudinal axis 20. The tubular sleeve 18 and body 17 are concentric and the sleeve is mounted for rotation about the axis of body 17. The body 17 of the muzzle brake has a central bore hole 7, of a diameter that is 0.020” – 0.030” larger than the diameter of the bullet or projectile (not shown) to be fired through the barrel of that particular rifle 15 which the muzzle brake is attached to. This central bore 7 is located in the generally central portion of the body 17 and extends through the body 17 on a longitudinal axis 20. Intersecting this central bore hole 7 are a series of machined ‘vents’ or ‘ports’ 13, and these openings act as gas escape paths to redirect the exiting propellant gas behind the projectile from the barrel bore 5 of the firearm 15 away at an angle of around 90 degrees (more or less), thus dissipating it from the central bore 7.

The tubular sleeve 18 is retained in place onto the cylindrical body 17 by a locking screw 12, which also locks the sleeve into correct rotational alignment. The tubular sleeve has a plurality of machined openings which correspond with the machined ports 13 in body 17 thus providing an escape path for the propellant gas and discharging it to the immediate atmosphere (see Figure 8 and Figure 9). Upon removal of locking screw 12 the tubular sleeve 18 may be rotated on the body 17 through an arc of 45 degrees, thereby blocking the gas ports 13 through the body 17. The openings in sleeve 18 are moved by such rotation out of alignment with the corresponding port holes 13, bringing the solid sections of tubular sleeve 18 into alignment with ports 13, effectively blocking the escape passage for the propellant gases. There is a secondary hole 12a in tubular sleeve 18 which permits the locking screw 12 to be re-installed with the sleeve 18 in this second position of relative rotation. It will be readily appreciated that with the adjustable muzzle brake set and locked in this non-functioning position (as shown in Figure 16), the rifle can be used in conventional fashion with no increased noise or blast effect, and the projectile and all of the propellant gases will exit though the borehole 7. Testing has confirmed that the bullet impact grouping on the target is essentially the same, regardless of whether the sleeve 18 is secured into either the primary or secondary positions of relative rotation.

In operation if the shooter desires to utilise the recoil-reducing capabilities of the muzzle brake then they will rotate and set the sleeve 18 to the primary position of relative rotation (as shown in Figures 2-15) and install the locking screw 12 through said sleeve and into the main cylindrical body 17, thereby locking the sleeve 18 into position both radially and axially.

When the firearm 15 is discharged, the projectile (bullet) passes out of the barrel bore 5 of the firearm 15 and through the central bore 7 of the muzzle brake 6a 6b of the present invention. As the projectile passes through the muzzle brake 6a 6b the propellant gas is restricted in its’ forward direction by the projectile itself, and as such when the bullet enters and passes through the first or primary ‘gas expansion chamber’ 9 (see Figure 9) the preferably machined ‘ports’ or ‘vent holes’ 13 in the body 17 of the muzzle brake 6a 6b provide a path of less resistance for the pursuing gases, and a percentage of the extremely high-pressure propellant gas is therefore released out through those vents 13 as shown by the arrows in Figure 9.

As the bullet continues to travel forward it passes through a clearance hole in a solid wall- section between the vents 13, known to those familiar in the art of muzzle brakes, as a ‘baffle’ 14 (see Figure 3 and Figure 9). The width of this baffle wall must be thick enough to withstand the pressure of the impacting forces of the gas blast impinging upon it. A thicker wall also increases the ‘dwell time’ or ‘plugging effect’ of the bullet as the bullet/projectile travels through it. This means also that bullets that are ‘long for calibre’ (i.e. more than 3 or 4 times longer than their diameter) can increase the time that the projectile blocks the path of the pursuing gas. The more gas that is directed out of the radial vents 13, the greater the reduction in recoil effect that would normally be experienced due to the unrestricted forward-motion of the exiting propellant gas.

The bullet travels through the initial ‘baffle’ wall where it enters the secondary ‘gas expansion chamber’ 10, and as it clears the secondary expansion chamber 10 it passes through the secondary baffle wall. Once again, the pursuing gases (those which have not already been released through the vents connected to the initial ‘gas expansion chamber’, are now diverted and released through the vents 13 connected to the secondary gas expansion chamber 10. As the projectile travels though the secondary baffle 14 wall the forward passage of the pursuing gases are temporarily blocked once again, until the projectile then enters the tertiary ‘gas expansion chamber’ 11. Whether there are three, or four, or more gas expansion chambers, the process continues until the projectile clears the muzzle brake 6a 6b and continues on its’ path to the target.

The present invention in preferred forms has a graduated gas-expansion chamber size for example as shown in Figures 3, 6 and 9. Moving from the rear end 16 of the muzzle brake 6a and 6b it can be seen that primary chamber 9 is smaller than the secondary chamber , which in turn is smaller than the tertiary chamber 11.

Tests conducted by the applicant have shown that for a muzzle brake 6a or 6b with three or four gas expansion chambers, and consisting of ports 13 that vent out the propellant gas radially, that a muzzle brake consisting of at least three expansion chambers with the primary chamber 9 being of the same width as, or are greater in width than, the bore 5 diameter of the firearm being fired, and with the other chambers proportionally increasing in size, will produce a greater gas-stripping and recoil reduction effect for it’s given size or length. This is compared with a brake that has four (or five or more) smaller chambers and vents, all being of the same/equal size, even if the combined volume of those smaller ports/vents is greater than the combined volume of the port/vent design so described in this invention.

A further feature of the present invention muzzle brake 6a and 6b are gas ports/vents 13 that angle back at approximately 5 to10 degrees, as shown in Figure 3 and Figure 9, from perpendicular to the central longitudinal axis 20 (bore line), towards the shooter/operator.

This gives an additional recoil energy reduction of approximately 3% for each 5 degree increase in angle back from perpendicular towards the shooter. This is also partially dependant on the effective outer diameter of the muzzle brake body 17 or baffle wall 14.

An additional feature that may be incorporated into those muzzle brake designs that have equi-spaced ports/vents around the circumference of the muzzle brake body is a self- tightening feature. The port holes 13 are offset (to the left side for a right hand thread and vice versa) from intersecting with the centreline of the longitudinal axis 20 of the muzzle brake 6a 6b, by an amount of approximately 0.040”. This causes the gasses to vent out slightly eccentrically, creating a self-tightening effect of the muzzle brake onto a conventional right-hand threaded muzzle 3. This is a useful feature, especially on firearms where the muzzle brake may need to be removed regularly for cleaning or to be replaced with another muzzle attachment such as a silencer or grenade launcher, and so that the muzzle brake will not shoot loose with repetitive firings. A further feature is that it will not be necessary to permanently secure the muzzle brake onto the barrel thread with products such as Loctite® or other thread-bonding systems, and as such will still be removable easily with moderate hand-pressure, and without the need to employ tools to aid the removal of the muzzle brake 6a 6b from the firearm 15.

In the preferred form of the invention the smallest ‘gas expansion chamber’ is of a width equivalent to, or slightly less than, the diameter of the bore 5 of the firearm 15 that the muzzle brake 6a 6b is fitted to. The largest ‘gas expansion chamber’ is to be larger than the bore diameter, achieving maximum efficiency at a width approximately 1.2x the diameter of the barrel/bore 5. In the preferred form the gas ports/vents 13 allow for a discharge of the propellant gas at an angle of approximately 10 degrees to the rear (towards the shooter). When fitted to the barrel of a rifle by the gunsmith, the muzzle brake must be installed in correct alignment and ‘indexed’ so that the top central line of the muzzle brake corresponds with the top central line of the rifle/system.

In the case of the muzzle brake 6a 6b as shown in Figures 2-18, the unique features of this design are that the rotating milling cutter is plunged in gradually at an angle of approximately 10 degrees back toward the rear end, to a depth only so far as the centreline central axis 20 of the muzzle brake body. The cutter then remains in this position, and the work-piece is moved transversely either back or forth along it’s longitudinal axis, in a manner which will form an elongated port/vent, as is required. This process is repeated for all of the angled ports as required to provide a graduated chamber size, from rear to front of the muzzle brake body in a progression of small-to-large.

The ports in the examples shown in Figure 2 – Figure 18 as earlier described may be deliberately machined slightly to the left of the central axis 20 of the body of the muzzle brake 6a 6b. This is machined as above with the variation in position of the milling cutter to achieve the eccentricity. In the case of radial ported muzzle brake 6b designs (those designs exhibiting port holes around the complete circumference of the muzzle brake body or sleeve), the ports may be machined approximately 0.040” to the left of the centreline central axis, and as such the discharged propellant gas creates a self-tightening effect for a right-hand threaded muzzle joint, or vice versa. The muzzle brake 6a 6b has a series of proportionally graduated gas expansion chambers, along with the proportionally associated connecting vents or ports 13, in a progressive form from small chamber to large chamber, along the length of the muzzle brake body 17 and the attached sleeve 18.

Figures 17 and 18 show a variation of the muzzle brake of the present invention which has been designed to permit changing of the position of relative rotation of the sleeve 18 to either the primary or secondary positions without the use of any tools being required to perform this function. In practice this allows the shooter to convert the muzzle brake function to either the ‘on’ or ‘off’ positions relatively quickly and easily. In this adaption of the current invention the cylindrical body 17 is longer than those shown in Figures 2 through 16, and the tubular sleeve 18 is retained onto the body 17 by a knurled and threaded end-cap 21, which is tightened on to the front end of the body 17 by hand. A cylindrical locating pin 22 is inserted into the body 17, which is employed to locate the sleeve 18 into either the primary or secondary positions of relative rotation, and when the knurled end-cap 21 is screwed onto the front end of the body 17 until it stops and pulls up tight on the front end of sleeve 18, the locating pin 22 prevents the sleeve 18 from rotating inadvertently when the rifle is fired. Thus there is no requirement for a permanent locking screw 12 on this muzzle brake. By simply unscrewing the threaded end-cap 21 a few turns, the shooter then pulls the sleeve forward slightly, rotates it through 45 degrees to the desired position, pushes the sleeve 18 back into alignment with either of the two machined notches in the rear end of the sleeve 18 into mating contact with the locating pin 22, and finally the knurled threaded end-cap 21 is screwed tightly back against the sleeve 18. Thus the operation of engaging or disengaging the muzzle brake braking function is so performed without the need of any special tools.

Both variations of the adjustable muzzle brake 6a and 6b so described in this specification also utilise two gas-sealing rubber O-rings, which are housed in circular grooves 19 which are machined into the cylindrical body 17, to a depth which causes the installed O-ring to provide a snug fit between the body 17 and the sleeve 18 at both the front and rear ends of the tubular sleeve 18. This helps to prevent unwanted high-pressure gas leakage out between the outer surface of the cylindrical body 17 and the front and rear ends of the installed tubular sleeve 18.

It is known by those who are familiar in the art of muzzle brake design and function, that the highest percentage of measured recoil reduction is usually achieved when testing muzzle brakes on rifles with those larger capacity ‘magnum calibre’ chamberings such as the commonly used 7mm, .30”cal., and .338” calibre magnums. The percentage of recoil reduction measured when testing muzzle brakes with smaller, more efficient cartridges, or when testing rifles with longer barrels, is generally less. In other words, those firearms that utilise cartridges which are as ‘ballistically efficient’ as possible, in the test firearm, will achieve a lesser recoil reduction when fitted with a gas-deflecting muzzle brake, compared with those less efficient barrel/cartridge combinations. The results of the testing regime conducted by the applicant confirm these earlier theories.

The muzzle brake of the present invention is so designed with the progressive gas expansion chamber/port sizes that it enables a more efficient and effective reduction in recoil forces compared with a muzzle brake of more conventional porting design or construction for an equivalent length and outer diameter. The result is an increase in efficiency of a muzzle brake that reduce recoil forces as much as possible for it’s given size.

The muzzle brake of the present invention has the advantages of improving the accuracy of the sporting or military rifle due to the equal and balanced stripping-off of propellant gases, as well as the harmonic stabilisation effect that the added weight/mass on the muzzle of a barrel often provides, being safe and easy to use, and does not direct too much severe gas blast or noise back directly at the shooter/operator when the outer sleeve is set in the ‘ports open’ position, and can be functionally disabled if desired while still being attached to the barrel of the firearm. On certain models that may need to be removed and re-fitted regularly, the invention provides vents/ports designed to create a self-tightening effect on a conventional right-hand threaded joint.

The foregoing description of the invention includes preferred forms thereof.

Modifications may be made thereto without departing from the scope of the invention.

Claims (6)

CLAIMS 1.. Having described the invention, what I claim is:

1. A muzzle brake, adapted for connection to the muzzle of a firearm, for a projectile to pass through, comprising or including: a cylindrical shaped body including, a rearward end for connection to said muzzle, a centrally located bore hole therethrough communicating from said rearward end to a forward end, at least three expansion chambers along and in communication with said borehole, each said expansion chamber separated by a baffle about said borehole, and each said expansion chamber in communication with at least four ports/vents on an outward surface of said cylindrical body, wherein said expansion chambers and their associated ports/vents are of progressively differing size to each other, with the largest chamber and associated ports being towards the front end of the muzzle brake; a tubular sleeve being telescoped over said cylindrical shaped body, the sleeve having a plurality of openings disposed for alignment with each of said ports/vents of said cylindrical body to permit propellant gas escaping from said openings to exit the muzzle brake when the sleeve is in one position of rotational alignment with respect to the cylindrical body, and there being a corresponding opening alignable with each port/vent hole, respectively, the body having areas without port/vent holes which are alignable with said openings which acts to prevent propellant gas escaping through said openings when the sleeve is in this second position of rotational alignment with respect to the cylindrical body; and a means of mounting the cylindrical body and the sleeve in said telescoped relationship for selective manual movement of the sleeve between one position and said second position.

2. A muzzle brake as set forth in claim 1 wherein said vents angle back toward said rearward end.

3. A muzzle brake as set forth in claim 2 wherein both the cylindrical body and the tubular sleeve are rigid, and the sidewall of said cylindrical body is substantially thicker than the sidewall of said sleeve so that the opening vents through the body are longer than the openings though the sleeve, whereby more force from the exiting propellant gases are applied to the stationary body than are applied to the moveable sleeve.

4. A muzzle brake as set forth in claim 3 wherein the tubular sleeve and cylindrical body are locked into desired rotational alignment with respect to each other with a locking screw, as defined with reference to any one or more of figures 2 to 16.

5. A muzzle brake as set forth in claim 3 wherein the tubular sleeve and cylindrical body are locked into desired rotational alignment with respect to each other with a locating pin and a threaded end-cap or nut, as defined with reference to figures 17 and 18.

6. A muzzle brake as herein defined with reference to any one or more of