Reduced-energy cartridge with exterior sealing member for fluted chamber

A reduced-energy cartridge for a chamber of a firearm includes a case and a sabot. The sabot is moveably attached to the case and supported for movement relative to the case from an unfired position to a fired position resulting from combustion within the combustion chamber. The cartridge further includes a sealing member that projects radially outward from the longitudinal axis and from the sabot. The sealing member defines a blowback boundary where the cartridge is configured to seal against an inner surface of the chamber of the firearm. A forward area of the cartridge and a rear area of the cartridge are separated by the blowback boundary. The sealing member is configured for releasably sealing against the inner surface of the chamber to regulate pressure at the forward area resulting from combustion within the combustion chamber.

TECHNICAL FIELD

The following generally relates to a cartridge for a firearm and, more particularly, relates to a reduced-energy cartridge with an exterior sealing member for a firearm with a fluted chamber.

BACKGROUND

Firearm cartridges are available in a wide variety of configurations. Some are configured for blowback operation. Usually, in configurations that rely on blowback operation, the breech is not locked mechanically at the time of firing. Once open, the cartridge or cartridge case is ejected.

The cartridge should perform reliably during such operations. Specifically, the casing should be well-supported in the chamber during firing. As such, pressure in the chamber can be effectively applied for both driving the projectile out of the barrel and for recoiling the bolt assembly.

However, conventional cartridges suffer from various limitations and/or deficiencies. For example, the material of the casing may be relatively expensive and/or the material may be relatively heavy. Other materials may not possess needed characteristics (e.g., thermal expansion characteristics) for reliable operation.

Also, some cartridges may include features that intentionally limit energy and speed of the projectile. The features of these so-called reduced-energy cartridges may, however, offset the balance of pressures necessary for effectively projecting the projectile and ejecting the ignited cartridge due to blowback.

Moreover, some cartridges may be ill-suited for firearms with chambers that include surface features. For example, fluting in the chamber may negatively offset the balance of pressures necessary for blowback operation of some cartridges.

Accordingly, it is desirable to provide an improved cartridge, such as a reduced-energy cartridge for a firearm that reliably provides blowback operation, even in a fluted chamber. Furthermore, it is desirable to provide a cartridge with materials that are lower cost, lighter in weight, etc. as compared to standard materials. Moreover, it is desirable to provide a cartridge that robustly supports a projectile to bring it up to the desired speed and energy (including for reduced-energy configurations) and that also reliably ejects from the chamber in a blowback operation. Furthermore, other desirable features and characteristics of the various embodiments described herein will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

A reduced-energy cartridge for a chamber of a firearm is disclosed. The cartridge includes a case and a sabot with a first end and a second end that are separated along a longitudinal axis. The first end is attached to the case to cooperatively define an internal combustion chamber with the case. The sabot is moveably attached to the case and supported for movement relative to the case from an unfired position to a fired position resulting from combustion within the combustion chamber. The second end extends from the case along the longitudinal axis in the unfired and fired positions. The cartridge further includes a sealing member that is provided on the second end of the sabot. The sealing member projects radially outward from the longitudinal axis and from the sabot. The sealing member defines a blowback boundary where the cartridge is configured to seal against an inner surface of the chamber of the firearm, wherein a forward area of the cartridge and a rear area of the cartridge is separated by the blowback boundary. The sealing member is configured for releasably sealing against the inner surface of the chamber to regulate pressure at the forward area resulting from combustion within the combustion chamber.

Furthermore, a method of manufacturing a reduced-energy cartridge for a chamber of a firearm is disclosed according to example embodiments. The method includes attaching a first end of a sabot to a case to cooperatively define an internal combustion chamber with the case, including moveably attaching the sabot to the case and supporting the sabot for movement relative to the case from an unfired position to a fired position. The sabot includes a second end that is separated from the first end along a longitudinal axis. The second end extends from the case along the longitudinal axis in the unfired and fired positions. The method also includes providing a sealing member on the second end of the sabot. The sealing member projects radially outward from the longitudinal axis and radially outward from the sabot. The sealing member defines a blowback boundary where the cartridge is configured to seal against an inner surface of the chamber of the firearm. A forward area of the cartridge and a rear area of the cartridge are separated by the blowback boundary. The sealing member is configured for releasably sealing against the inner surface of the chamber to regulate pressure at the forward area resulting from combustion within the combustion chamber.

Moreover, a reduced-energy cartridge for a fluted chamber of a firearm is disclosed according to example embodiments. The cartridge includes a case and a sabot. The sabot includes a first end and a second end that are separated along a longitudinal axis. The sabot includes a combustion passage extending longitudinally between the first end and the second end. The first end is attached to the case to cooperatively define an internal combustion chamber with the case. The first end is supported for movement relative to the case from an unfired position to a fired position resulting from combustion within the combustion chamber. The second end extends from the case along the longitudinal axis in the unfired and fired positions. The second end has a frustoconic datum taper. Also, the cartridge includes a sealing member that is provided on the second end. The sealing member projects radially outward from the longitudinal axis and radially outward from the sabot. The sealing member defines a blowback boundary where the cartridge is configured to seal against a fluted inner surface of the chamber of the firearm. A forward area of the cartridge and a rear area of the cartridge are separated by the blowback boundary. The sealing member is configured for releasably sealing against the fluted inner surface of the chamber to regulate pressure at the forward area resulting from combustion within the combustion chamber.

DETAILED DESCRIPTION

Various embodiments contemplated herein relate to cartridges (e.g., reduced-energy cartridges) for firearms that are configured for blowback operation. In some embodiments, these cartridges may be used as training ammunition for firing relatively low-mass projectiles. Cartridges of the present disclosure may include one or more features that improve cycling of a weapon (the action of expelling spent cartridges (or casings) from a firearm and subsequently loading a fresh round into the firing chamber) while maintaining performance of the projectile (e.g., maintaining energy to the projectile and projectile speed to within predetermined limits).

Referring initially toFIG.1, a cartridge100for a firearm is illustrated according to example embodiments of the present disclosure. The cartridge100may be of any suitable caliber. The cartridge100may also be configured in different ways for different firearms. It will be appreciated that the term “firearm” is used generally herein to mean any weapon suitable for firing the cartridge100, including, but not limited to, a handgun, long gun, rifle, shotgun, carbine, machine gun, submachine gun, etc. Also, the cartridge100may be configured for firearms, including but not limited to those that are single-shot, repeating-action, semi-automatic or select-fire/fully automatic. In some embodiments, for example, the cartridge100may be configured as a 7.62×51 mm NATO cartridge and for firearms that are configured for such cartridges.

Generally, the cartridge100may define a longitudinal axis102that extends between an aft end104and a forward end106. It will be appreciated that a forward direction is defined along the axis102from the aft end104toward the forward end106. On the contrary, a rearward direction is defined along the axis102from the forward end106toward the aft end104.

Also, the cartridge100may include a casing111and a projectile114, which is removably attached to the casing111. However, it will be appreciated that the cartridge100of the present disclosure may include the casing111(and propellant therein) and that the projectile114may be omitted (e.g., when the cartridge100is configured as a blank).

The casing111may include a case110and a sabot112. The case110may be disposed at the aft end104, and the projectile114may be disposed at the forward end106. The sabot112may be disposed longitudinally between the case110and the projectile114. The sabot112may be moveably attached (e.g., slidably attached) to the case110, and the sabot112may be removably attached to the projectile114.

As shown inFIG.2, the case110may be cylindrical and hollow with one substantially closed end and one open end. The case110may include an end cap115at the aft end104. The end cap115may include a radially-projecting (flange-like) rim116. The end cap115may also include a primer cap opening120that is centered on the axis102. The case110may also include a hollow side wall117that is centered about the axis102and that projects from the end cap115along the axis102. As such, the side wall117and end cap115cooperatively define an internal cavity118of the case110. The side wall117may include a terminal end123with an outer diameter area that tapers downward in radius and an inner diameter area with an annular groove127. The case110may be made from an aluminum-based material (e.g., aluminum or an aluminum alloy) in some embodiments; however, it will be appreciated that the case110may be made out of another material without departing from the scope of the present disclosure.

The sabot112may be elongate and cylindrical with a first end124and a second end126that are separated along the axis102. Furthermore, the sabot112may include a central passage147that is centered on the axis102and that extends continuously through the sabot112from the first end124to the second end126. The sabot112may include a shaft portion125disposed forward of the first end124and having a smaller radius than the rest of the sabot112. The shaft portion125may slide within the terminal end of the case110. The sabot112may additionally include a central longitudinal portion128with an annular body132having a larger radius than the rest of the sabot112and a forward body134with a comparably smaller radius. The forward body134may be disposed closer to the forward end106, and the annular body132may be disposed closer to the aft end104. The sabot112may include a taper136that gradually transitions between the annular body132and the forward body134. Additionally, the sabot112may include a datum taper138. The datum taper138may taper gradually downward as the datum taper138extends longitudinally and transitions from the forward body134to the second end126of the sabot112.

The second end126may further include a geometrical groove142. The groove142may be annular in some embodiments, but the geometry of the groove142may be configured otherwise without departing from the scope of the present disclosure. The groove142may be disposed at a distance189from the datum taper138. In some embodiments, the groove142may be disposed forward relative to the datum taper138as shown inFIG.4. In other embodiments, the groove142may be disposed rearward relative to the taper138. Moreover, in some embodiments, the groove142may be disposed on the taper138.

The sabot112may further include a longitudinally directed annular flange140that defines the terminal portion of the second end126. The flange140may receive the projectile114in some embodiments (FIG.2).

The sabot112may define a unitary, one-piece member. The sabot112may also be made from and/or include an aluminum-based material (e.g., aluminum or an aluminum alloy) in some embodiments. However, other materials may be used without departing from the scope of the present disclosure.

A sealing disc145may be included proximate the first end124of the sabot112. The sealing disc145may be fixedly attached to the first end124, and the sealing disc145and first end124may include interlocking features, such as corresponding undercut radial surfaces. The sealing disc145may include a choke aperture150that is centrally located and that is centered on the axis102. The choke aperture150extends through the sealing disc145to fluidly connect the combustion chamber152and the passage147. The choke aperture150may include an inlet directed toward the aft end104. The choke aperture150may also include an outlet that tapers outward as it extends toward the forward end106. It will be appreciated that the dimensions of the inlet, the taper of the outlet, and/or other characteristics of the choke aperture150may be selected and configured for managing and controlling combustion within the cartridge100and for metering the quantity of gases directed to the projectile to control its speed and metering the quantity of gases for recoiling the weapon.

The first end124of the sabot112(including the sealing disc145) may be received in the case110. The sealing disc145may have an outer diameter disposed at an inner diameter of the case110to substantially seal thereto. The sealing disc145, the first end124, and the shaft portion125of the sabot112may be supported for sliding movement within the cavity118of the case110such that the case110and sabot112may move telescopingly relative to each other between an unfired position (FIG.2) and a fired position (FIG.3). In the unfired position, the terminal end123of the case110may be disposed adjacent the annular body132and the first end124may be retracted within the case110as represented inFIG.2. Moving to the fired position represented inFIG.3, the shaft portion125may extend, slide, and project out of the case110.

The first end124of the sabot112with the attached sealing disc145may cooperate with the case110to define an internal combustion chamber152. As the sabot112slides relative to the case110, the volume of the chamber152changes. The volume in the chamber152grows as the sabot112and case110move from the unfired position toward the fired position.

The cartridge100may further include a propellant charge160(FIG.2). The propellant charge160may include a propellant162(gunpowder or cordite) included in the chamber152. The propellant charge160may also include a primer122within the primer cap opening120.

During a firing sequence, the primer122may ignite the propellant162to telescopingly move the cartridge100from the unfired position (FIG.2) to the fired position (FIG.3). As represented inFIG.3, the choke aperture150regulates and controls distribution of the pressure that builds through central passage147for driving the projectile114and bringing the projectile114up to velocity as it exits the barrel of the firearm. It will be understood that the telescoping movement of the sabot112and case110may reduce or limit energy for the projectile114as compared to a cartridge with a rigid or fixed casing.

The cartridge100may further include a sealing member170. In some embodiments, the sealing member170may be an independent part that is removably attached to another part discussed above. For example, as shown inFIGS.1-4, the sealing member170may be a part that is removably attached to the sabot112. However other embodiments of the sealing member may be integrated into another part. For example, as shown inFIGS.5-6, the sealing member may be part of the sabot.

As shown in the embodiments ofFIGS.1-4, the sealing member170may have a predetermined geometrical shape, such as an annular or toric shape; however, the sealing member170may have another shape without departing from the scope of the present disclosure (e.g., the shapes discussed below with reference toFIGS.5and6). The sealing member170may be configured for substantially sealing against an inner surface180of a chamber182of a firearm184as will be discussed with reference toFIGS.3and4. The sealing member170may have a wide variety of configurations for sealing to the inner surface180during action of the firearm. The sealing member170may regulate pressures for driving the projectile114up to speed and for blowback self-ejection of the case110and sabot112from the chamber182.

It will be appreciated that the seal of the sealing member170against the inner surface180is a temporary seal created during blowback operation. The sealing member170provides a seal and gas flow obstruction, thereby creating a significant pressure gradient between a forward area198and a rear area197of the cartridge100(FIGS.3and4) as will be discussed in greater detail below.

The sealing member170may have one of a variety of geometrical shapes, such as an annular shape, a toric shape, a toroidal shape, etc. Thus, the sealing member170may extend continuously about the axis102. The sealing member170may be centered on the axis102.

The sealing member170may also have a solid cross section. For example, the sealing member170may have a solid, circular cross section in some embodiments. However, the sealing member170may have another cross sectional shape without departing from the scope of the present disclosure. The sealing member170may be constructed from a resilient material. For example, the sealing member170may be made from a resilient polymeric material such as nitrile rubber (i.e., Buna-n rubber); however, the sealing member170may be made of other materials without departing from the scope of the present disclosure. Accordingly, the sealing member170may resiliently flex to provide sealing.

The sealing member170may be received and disposed within the continuous, annular groove142of the sabot112. Accordingly, the sealing member170may be disposed in a forward direction and spaced apart slightly at a distance189from the frustoconic datum taper138with respect to the axis102. In other embodiments, the sealing member170may be disposed in a rearward direction from the datum taper138, or the sealing member170may be disposed on the datum taper138in further embodiments.

Also, the sealing member170may project outward radially from surrounding areas of the outer surface of the sabot112. As shown inFIGS.3and4, an outer radius190of the sealing member170may be approximately the same or only slightly larger than an outer radius192of the second end126of the sabot112. Thus, the outer radius190may be slightly larger than that of the datum taper138.

As mentioned, the sealing member170may be operable and configured to seal against the inner surface180of the chamber182. More specifically, while the cartridge100is in the unfired position, the datum taper138may nest against an inversely corresponding tapered chamber surface193of the inner surface180while the sealing member170seals against a forward portion183of the inner surface180of the chamber182. The diameter of the forward portion183may remain substantially constant along its longitudinal length.

In some embodiments, the sealing member170may be useful for sealing against a surface feature included on the inner surface180. For example, in some embodiments, the inner surface180may be fluted (i.e., may include one or more flutes194). The flutes194may be shallow grooves that extend primarily in the longitudinal direction along the axis102. In some embodiments, the flutes194may extend straight or tapered in all direction and substantially parallel to the axis102, and there may be a plurality of flutes spaced apart equally about the axis102in a circumferential direction. However, in additional embodiments, the flutes194may extend primarily along the axis102but also slightly helically about the axis102.

The flutes194may extend along the tapered chamber surface193and to the forward portion183. The sealing member170may seal against the uneven, fluted forward portion183as represented inFIG.3. For example, the radial dimensions of the sealing member170, the resilient flexibility of the sealing member170, the position of the sealing member170relative to the datum taper138, and/or other characteristics of the sealing member170may allow the cartridge100to achieve the seal. The sealing member170may achieve the balance of pressures for driving the projectile114and for blowback of the empty cartridge (i.e., the case110and sabot112in the fired position).

Operation of the sealing member170will now be discussed in greater detail. Assuming the cartridge100is in the unfired position ofFIG.2. The cartridge100may begin cycling, and in some embodiments, may move from a magazine into the chamber182. A bolt assembly may apply a forward-directed force (represented by arrows195inFIG.3) on the end cap115, and the force195may be provided by a recoil spring of the bolt assembly in some embodiments. This force195may push and substantially seal the sealing member170against the fluted forward portion183of the inner surface180. As such, the sealing member170may define a blowback boundary199of the cartridge100. The blowback boundary199may be defined where the sealing member170abuts and seals against the inner surface180. As such, the forward area198of the cartridge100and the rear area197of the cartridge100are separated longitudinally by the blowback boundary199. It will be appreciated that the blowback boundary199may move relative to the inner surface180as the cartridge100and the sealing member170move from the unfired position to the fired position and as the pressures in the chamber182change. More specifically, the blowback boundary199may move rearward from the forward portion183of the inner surface180to the tapered chamber surface193and further rearward during blowback operations.

The propellant charge160may be ignited, generating gas pressure that pushes the projectile114out of the barrel. Some of the generated gas pressure in the forward area198(represented at196inFIG.4) pushes rearward on the sabot112. The pressure196pushes against the sealing member170and back against the sabot112and case110in the fired position (FIGS.3and4). The pressure196, therefore, pushes back the bolt carrier assembly, which recoils the firearm, and once the breech is open, the empty cartridge (i.e., the case110and sabot112) eject. Furthermore, a fresh cartridge100(in the unfired position) may move into the chamber182, for example, from the magazine.

The sealing member170effectively seals against the inner surface180of the chamber182, even in embodiments where the inner surface180is fluted. Also, even in embodiments where the cartridge100is a reduced-energy cartridge100(i.e., where forces are relatively low), the sealing member170provides the proper balance of pressures for bringing the projectile114up to the desired speed and for blowback ejection of the empty cartridge.

In addition, embodiments may include a sabot112and a case110that have relatively low thermal expansion characteristics. For example, as mentioned, the sabot112and case110may be made of aluminum in some embodiments in order to reduce weight of the cartridge100and to reduce material costs. However, it will be appreciated that the sabot112and/or case110may be made from other materials (e.g., brass, steel, etc.) without departing from the scope of the present disclosure.

The sealing member170also provides manufacturing benefits. For example, because of the features discussed above, the cartridge100may be manufactured efficiently.

Referring now toFIGS.5and6, the cartridge200is shown according to additional embodiments of the present disclosure. The cartridge200may be substantially similar to the embodiments discussed above except as noted. Components that correspond to those ofFIGS.1-4are indicated by corresponding reference numbers increased by 100.

The cartridge200may include a case210, a sabot212, and a projectile214. Furthermore, the cartridge200may include a sealing member270. The sealing member270may include a plurality of elongate rails271(i.e., ribs, spines, ridges, etc.). In some embodiments, there may be six rails271; however, the cartridge200may have any number of rails271without departing from the scope of the present disclosure. The rails271may be attached to the sabot212and may extend longitudinally along the outer surface thereof. In some embodiments, the outer surface of the rails271may define a taper. In the illustrated embodiment, the rails271extend substantially parallel to the axis202. Also, the rails271may be spaced apart equally about the axis202in the circumferential direction.

In some embodiments, the rails271of the sealing member270may be integrally attached to the sabot212so as to define a unitary (i.e., one-piece) body. For example, the sabot212and rails271may be integrally attached to define a unitary polymeric body (i.e., a polymeric one-piece body). However, it will be appreciated that the body may be made out of different materials without departing from the scope of the present disclosure.

The sealing member270may also define intermediate surfaces272located circumferentially between neighboring rails271. The intermediate surfaces272may be substantially smooth and the rails271may project out radially therefrom. Furthermore, in some embodiments, the rails271and/or the intermediate surfaces272may extend to the datum taper238. The rails271and/or the intermediate surfaces272may additionally extend to the flange240of the sabot212.

As shown inFIG.6, when the cartridge200is disposed in the chamber282of the firearm284, the rails271may be received within corresponding ones of the flutes294. The flutes294and the rails271may, thus, have inverse contour, shape, etc. and may have a male-to-female configuration. During firing, the rails271and the intermediate surfaces272may deform to thereby seal against the inner surface280. In some embodiments, the rails271, the intermediate surfaces272, and/or other portions of the sabot212may plastically (i.e., permanently) deform to create the temporary seal discussed above. As such, the projectile214may achieve the desired velocity and the spent cartridge200may be ejected in the blowback operation as discussed above.

Referring now toFIG.7, the cartridge300is shown according to additional embodiments of the present disclosure. The cartridge300may be substantially similar to the embodiments discussed above except as noted. Components that correspond to those ofFIGS.1-4are indicated by corresponding reference numbers increased by 200.

The cartridge300may include a case310and a sabot312. The cartridge300may also include a sealing member370. The sealing member370may be an O-ring, similar to the sealing member170ofFIGS.1-4. The sabot312may include a pointed end. The cartridge300may function as discussed above as a reduced-energy cartridge. However, the cartridge300may be configured as a blank cartridge (with no projectile).

Referring now toFIG.8, the cartridge400is shown according to additional embodiments of the present disclosure. The cartridge400may be substantially similar to the embodiments discussed above except as noted. Components that correspond to those ofFIGS.1-4are indicated by corresponding reference numbers increased by 300.

The cartridge400may include a case410and a sabot412. The cartridge400may also include a sealing member470. The sealing member470may include a plurality of elongate rails, similar to the sealing member270ofFIGS.5and6. The sabot412may include a pointed end. The cartridge400may function as discussed above as a reduced-energy cartridge. However, the cartridge400may be configured as a blank cartridge (with no projectile).