US 3528336 A
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United States Patent  Inventor Fredrik Donner Helsinki, Finland  Appl. No. 716,519  Filed March 27, 1968  Patented Sept. 15, 1970  Assignee OyTampella AB Tampere, Finland  Priority April 1, 1967  Germany  0 12403  MUZZLE ASSEMBLY FOR SMOOTH-BORE PROJECTILES 2 Claims, 4 Drawing Figs.
 U.S.Cl 89/14, 181/60  Int. Cl. F411 17/12  Field ofSearch 89/13, 1.35,1.816, 14,142, 14.3,l4.4;42/79; 181/3322, 36,57, 60, 61,68, 69, 70
 References Cited UNITED STATES PATENTS 933,098 9/1909 McClean 89/14(3)UX 1,380,358 6/1921 Cooke 89/14K3YUX Primary ExaminerBenjarnin A. Borchelt Assistant Examiner-Stephen C. Bentley Attorneys- Lowry, Rinehart, Markva and Smith ABSTRACT: A muzzle assembly for use at the end of a smooth-bore barrel on firearms such as mortars, grenade launchers and the like which fire smooth-bore, tin-stabilized projectiles. The muzzle assembly includes a radial opening section which has a plurality of disc members and spacer discs mounted at the end of the barrel. The spacer discs are located between the disc members to form outlet openings along the periphery of the assembly to exhaust firing gases therethrough. The disc members form an inner diameter along the entire length of the radial opening section. This inner diameter is substantially identical to the inner diameter of the barrel on the firearm. The outlet openings extend from the inner diameter of the radial opening section to the periphery of the assembly at an acute angle of inclination with respect to the trajectory of the projectile.
Patented Sept. 15, 1970 Sheet of 2 IN VE N TOR FIQEDR/k Don/N5? A Trys.
MUZZLE ASSEMBLY FOR SMOOTH-BORE PROJECTILES BACKGROUND OF THE INVENTION Various types of muzzle assemblies on rifled barrels for firearms are known. Generally, cage-like structures are involved, provided with radial openings of a greater or lesser size, and having a larger inner diameter than the barrel. Further, in muzzle assemblies the disposition of the openings for the explosive gases is so formed that the gases are to a greater or lesser extent deflected backwards.
Firearms such as mortars, grenade launchers and the like which fire smooth-bore, fin-stabilized projectiles are well known in the prior art. The barrels on these types of firearms are smoothbore so that the peripheral surface of the smoothbore projectiles contact the inner diameter surface thereof upon firing the firearm. The use of muzzle assemblies on such smooth-bore barrels is heretofore unknown in the prior art.
SUMMARY OF THE INVENTION The object of the invention is to make a barrel end or muz zle assembly, especially for smoothbore barrels, by means of which the passage of the projectile can be beneficially influenced. The barrel-end is characterised according to the invention in that radial openings are provided in the barrel or the assembly on the inner circumference of the barrel-end or muzzle assembly, having an identical inner diameter, corresponding to the barrel. The openings can be formed as annularly running grooves. In this instance the ,series of grooves can be spiral. Further, the openings can be formed as outletslots passing through the barrel or the assembly.
In this way considerable influence can be exercised on the trajectory of the projectile, in that its ballistic features are improved. As long as the fin-stabilised projectile is still in the barrel, the gas pressure behind the projectile lessens as a result of the openings or holes in the barrel-end or assembly. The gases can escape before the projectile has emerged from the barrel. In previous embodiments of the barrels of launchers and the like, the highly-compressed gases can still exert an influence on the fin-stabilised projectile. When the latter receives no further guidance from the barrel, it comes about, in the design according to the invention, that the barrel-end still guides the projectile, and yet the gases are considerably decompressed. Any disadvantages jet effect, when highlycompressed gases can affect the projectile when it is already free of the barrel, is excluded. The openings or holes in the barrel-end and the like are so distributed that contact of the projectile or its fin-assembly is maintained with the barrel up to the barrel-end. In the case of outlet-slots running longitudinally to the barrel-end, some fins of the fin-assembly are always in contact with the inner wall of the barrel-end or barrelextension. The design according to the invention of the barrelend and the like leads to an increased stabilising effect of the barrel on the projectile. The accuracy of the weapon is considerably increased. On average, the accuracy is twice as great as previously. The projectile itself is subject to less scatter. Further, the weapons stability is increased. The reduction or exclusion of the jet effect directly at the barrel mouth means that the projectile can achieve a higher muzzle velocity, resulting in a longer range. Besides, the named design of the barrelend or barrel-extension causes a quieter shot. This has the advantage of making it more difficult to discover the site of the weapon from the noise.
According to a further feature of the invention, the outletslots are preferably arranged at an inclination running at an acute angle to the direction of flight of the projectile. In this way the explosive gases can escape undisturbed in the effective direction. Turbulence and thereby sources of loss are avoided.
The construction of the muzzle assembly with oblique outlet slots is preferably done by the assembly of a number of obliquely-angled annular discs alternating with distance-discs. Thus a larger number of obliquely-running guide-surfaces and outlet slots for the explosive gases in the direction of the projectile trajectory are obtained. Further, the construction is characterised by its simplicity. The inner diameter of the annular discs should correspond to the inner diameter of the barrel.
Further, the annular discs can be assembled into a package" of discs with the distancediscs, in fact between a base-part and a head part. Connection is by anchor bolts passing through the discs. In this way one obtains a muzzle assembly made up of many single discs, as a unit which can be attached as a whole part to the barrel-end of the mortar or the like. So that the discs are locked on one another, a locking-rod can be passed through the discs. To this end, the holes in the discs designed to contain the anchor bolts can be provided with radial openings into which the locking rod, running parallel to the anchor bolt, is inserted. Such a muzzle assembly meets all the demands required of it, as a compact unit.
BRIEF DESCRIPTION OF DRAWINGS Other objects of this invention will appear in the following description and appended claims, reference being made to the accompanying drawings forming a part of the specification wherein like reference characters designate corresponding parts in the several views.
FIG. 1 is a longitudinal sectional view along line II-II of FIG. 2.
FIG. 2 is a partial sectional view along the line III III of FIG. 1.
FIG. 3 is a longitudinal view partially in cross-section of another embodiment of a muzzle assembly made in accordance with this invention; and
FIG. 4 is a sectional view along the line IV- IV of FIG. 3.
DESCRIPTION OF SPECIFIC EMBODIMENTS An advantageous solution of the problem is realised in the specific embodiments. In the example in FIGS. 1 and 2 the muzzle assembly 20 has radial outlet-slots or openings 5c, which are arranged at an acute angle to the direction of flight 6 of the projectile, i.e. outwards and obliquely upwards. A large number of such slots 5c is preferably provided. The explosive gases issuing from the barrel are deflected obliquely upwards and outwards, all round, by the guide-surfaces limiting slots 5c, so that the gases are afforded clean and directed guidance. The withdrawal of the gases takes place in laminar fashion with a relatively smaller diversion from the flowdirection in the barrel, the angular deflection of the slots lying in the region of an acute angle to the projectiles path. The angle comes to about 45 degrees, for preference. Dependent on the result desired, the inclination of the slots can also be made slightly smaller, or slightly larger. The muzzle assembly is constructed so that it has a large number of annular disc members 7 which lie at the angle of-inclination provided. Spacer discs 8 are provided between the annular discs. A package" made up of these disc members and spacer discs is located between a correspondingly-designed base-part 9 and a head-part It). The whole is held together by anchor-bolts 11, so that a compact unit results. The assembly can be screwed on the thread 12 or barrel 1. Disc 13 grips under the projecting part of the barrel 1. The anchor-bolts 11 are screwed tight by nuts 14.
The spacer discs 8 are essentially plate-parts of restricted dimensions and breadth, so that an abundant free space 50 remains for the outlet-slot. The discs 8 are formed as favourable to flow in their contour, and are in essence droplike. So that the discs cannot move, their position is fixed by a lockingrod 15. To this end a radially-running opening 16 is provided, in each annular disc member 7 and in each spacer disc 8, locking-rod 15 being thrust through the said opening 16. Annular disc members 7 preferably have an inner diameter which corresponds to the clear diameter of barrel 1. In this way the muzzle assembly forms at the same time an extension of the barrel to guide the projectile. The surface of the outflow slots 50 becomes gradually greater with the forward movement of the projectile, as more slot openings are released. The gases directed outwards all round in quiet paths.
Ejdimen t inFlGS. 3 arid 4 spacer discs 17 have, at the outer end, extensions 18 which run more or less parallel with the longitudinal axis of muzzle assembly 2d in an arc. In this way the spacer discs 17 are locked on the anchor-bolts 1 1, so that the discs 17 cannot twist around the axis of the anchor bolts 11. In this way automatic twist-prevention for the discs is achieved. Muzzle assembly 2d corresponds in its construction to assembly 2c of FIGS. 1 and 2. Attachment to barrel 1 can be provided by means of a box nut 19, which is screwed in a corresponding way on the end of barrel 1.
1. A muzzle assembly for use at the end of a smooth-bore barrel on firearms such as mortars, grenade launchers and the like which fire smooth-bore tin-stabilized projectiles comprising:
a. means mounting a radial opening section including a plurality of disc members and spacer members on the end of said barrel;
b. said mounting means including a base portion, a head portion, at least one anchor bolt member and at least one locking rod memberj c. said base portion including means to connect the muzzle assembly to the end of the barrel at one end of the radial opening section;
d. said head portion being located at the other end of the radial opening section;
c. said spacer members being located between said disc members to formoutlet openings along the periphery of the assembly to exhaust firing gases therethrough;
f. said disc members forming an inner diameter along the entire length of the radial opening section, said diameter is substantially identical to the inner diameter of the barrel;
g. said disc members are annular and obliquely angled and form annular outlet openings therebetween;
h. said outlet openings extend from the inner diameter of said radial opening section to the periphery of the assembly at an acute angle of inclination with respect to the trajectory of the projectile;
. said anchor bolt member extends through said disc members and said spacer members to secure said radial opening section between said base and head portions; and
j said locking rod member extends through the spacer members to prevent turning of the spacer members about said anchor bolt member.
2. An assembly as defined in claim 1 wherein:
said spacer members are disc-shaped and have a hole located around each anchor bolt member;
each said spacer member hole includes a radially extending opening to fix the position of said spacer member at each locking rod member; and
each said locking rod member and each said anchor bolt member being parallel with respect to each other.