BACKGROUND OF THE INVENTION
This invention generally relates to firearms and ammunition, and specifically to a method of silencing firearm shots and the usage of subsonic bullets.
In military, hunting, or police circumstances, it is often-times desirable to silence firearm shots in order to mask the shooter's presence. One common way to achieve this is to use a sound suppressor that attaches to the end of a firearm barrel (U.S. Pat. No. 1,111,202). These dampen the sound of a firearm shot by lowering the exit pressure of the expanding gas and so muffling the sound of the chamber explosion. However, since most ammunition used in modern firearms is supersonic (having speeds faster than 343.2 m/s), a sonic boom is heard shortly after the bullet leaves the barrel, rendering the sound suppressor, in effect, useless, and the shooter's presence and location detectible.
In answer to this, attempts at using subsonic ammunition have been made (U.S. Pat. No. 5,822,904, U.S. Pat. No. 9,182,204). They achieve this by the use of less powder within the ammunition casing, causing less force to be applied to the bullet during firing, causing its flight speed to be below the speed of sound (343.2 m/s). However, no novel design thought has been given to the bullets used in these applications, which are still designed aerodynamically for supersonic flight. When these supersonic bullets are fired at subsonic speeds, they can be prone to tumbling and energy loss, which drastically affect the accuracy and precision of the shot.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a bullet consists of three main aerodynamic components that aid in subsonic flight: 1) a parabolic or hemispherical nose; 2) a cylindrical center length with parallel sides; 3) a parabolic into conical tail. This serves to reduce air pressure and turbulent airflow along the bullet during flight.
Still further, the bullet comprises in construction a copper shell, filled in the tail with a material having a density less than or equal to 3.0 g/cm3, and in the nose with a material having a density greater than or equal to 11 g/cm3. This puts the COM (center of mass) as far forward as possible, lending further stability to the bullet during flight.
The bullet is proportionally longer than is usual, allowing for both an increased bullet mass and for sufficient casing loading.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a representation of a prior art bullet.
FIG. 2 is a representation of one embodiment of the present invention.
FIG. 3 is a representation, in section, of one embodiment of the present invention.
FIG. 4 is a representation, partly in section, of a prior art bullet in use with a standard casing.
FIG. 5 is a representation, partly in section, of one embodiment of the present invention in use with a standard casing.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the accompanying figure, a subsonic bullet of the prior art is depicted in FIG. 1, and comprises a conical into parabolic nose [1] and tapered to flat tail [2], connected by a cylindrical portion with a diameter such that it fits snugly into a casing of the appropriate caliber. The aerodynamics of the prior art depicted in FIG. 1 is essential for supersonic flight; the pointed nose is used to reduce air pressure against the nose of the bullet with flight speeds in excess of the speed of sound. When used in subsonic applications, however, the pointed nose and flat tail cause pockets of air pressure buildups that increase the drag on the bullet and reduce its impact energy. In addition, the position of the COM (center of mass) [3] is far enough back in the bullet to cause a loss of stability at low flight speeds; even tumbling which can have a noticeably negative impact on both accuracy and precision when fired.
With reference to FIG. 2, an embodiment of the present invention is shown. It comprises of three aerodynamic features. The nose [4] is parabolic or hemispherical to reduce air pressure and drag at speeds below the speed of sound (343.2 m/s). For the same effect, the tail [6] is parabolic into conical to reduce turbulent airflow. The main body [5] is of equivalent diameter to that of the prior art in FIG. 1, for the same caliber, yet is proportionally longer than in the prior art, allowing the barrel rifling to more readily grasp the bullet. This causes the bullet to in about its roll axis (this case its length or axis of trajectory), and, due to the gyroscopic properties of angular momentum, fly more accurately. The forward location of the COM [7], combined with these described aerodynamic components, allows for a more stable flight at subsonic speeds over longer distances and with a flatter trajectory.
FIG. 3 illustrates one embodiment, in which an outer shell [9] of copper is filled with the two materials chosen for their physical properties. The tail [10] is filled with a material with a density less than or equal to 3.0 g/cm3, in this case aluminum. The nose [8] fills the rest of the bullet and is comprised of a material with a density greater than or equal to 11.0 g/cm3, in this case lead. These two materials lend two benefits to the invention. First, the distribution of the dense lead with the less dense aluminum achieves the desired location for the COM [7]. Second, the usage of the soft lead with the harder aluminum will cause deep target penetration while still expanding for sufficient damage.
When firing a bullet at subsonic speeds, less powder must be used than for supersonic speeds. When this is done in standard casings [13], as is common in current applications, air pockets are created within the casing. This can cause uneven burning of the powder, or if the void is between the primer [14] and the powder, delayed fire. When these happen, the shooter's reactions can open him to harm. To solve this (without using specialized casings as in U.S. Pat. No. 5,822,904), the bullet must be longer than in the prior art of FIG. 1 to fill more of the interior volume of a standard casing [13]. With reference to FIG. 4, when using the prior art [11] of FIG. 1, the tail of the bullet barely extends past the neck [12] of the casing [13]. However, with reference to FIG. 5, it can be seen that the invention [15] of FIG. 2 fills almost half of the casing [13], thus eliminating the voids in the powder. An added benefit to this increased length is that it allows the bullet to be heavier using the same materials. Since the flight energy of a bullet varies to the mass and square of the velocity [E=(½)mv2], the subsonic speed of the bullet drastically lowers the impact energy of the bullet, as compared to supersonic applications. Having a higher grain bullet helps alleviate this issue by linearly raising the flight, and so impact, energy of the bullet.
The invention here described of novel aerodynamics and construction has been shown to alleviate the problems inherent in subsonic ballistics, such as, but not limited to, tumbling in flight, loss of impact energy, as well as the changes in both accuracy and precision of firearm shots fired at subsonic speeds.
Patent Application
20170003107
