Abstract:
A firearm based breeching tool uses the expansion gases of a blank high capacity firearm round to fire a piston at a breeching chisel, the chisel having a cutting head that is designed to breech a hardened obstacle. The invention is based on an assault rifle configuration that is modified to use the pump action of a shotgun to replenish a round of ammunition into the firing chamber and otherwise reset the device including the firing piston and the standard trigger mechanism.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a breaching tool used to breach through an entry obstacle such as a deadbolt, safety chain, etc., wherein a cutting chisel or ram is operationally impacted onto the obstacle via the discharge force from a firearms ammunition blank fired by the device. The tool is reset and a new blank placed into the firing chamber from the firearm&#39;s magazine via pump action. 
     2. Background of the Prior Art 
     Both police and military personal are often called on to breach a barrier such as a door in order to gain access to an interior of a structure and capture the persons and/or contraband therein. Such a breach must be quick in order to prevent the potential bad guys within the structure from taking a defensive position and attacking those making entry. In a typical structure, such as a house that has a standard deadbolt door thereon, a simple kick in or the use of a small battering ram is usually sufficient to quickly overcome the entry barrier. However, often the entry barrier is hardened such that those seeking entry need more force to disable the entry obstacle than can be supplied by human power alone. In such situations an appropriate machine is called upon to overcome the barrier obstacle. 
     One method employed to overcome a hardened entry barrier is to use a vehicle. A line, typically a cable or a chain, is tied to the entry obstacle with the other end tied to the vehicle. A winch on the vehicle or the locomotive power of the vehicle itself is used to pull the entry barrier away from the structure and allow personnel to enter. While this method works-quite well in many situations, it is not without its shortcoming. The use of a vehicle requires time to extend the cable or chain between the vehicle and the entry barrier which time can cause the occupants of the structure to detect the operation being performed and the element of surprise vanishes. Additionally, many doors are configured such that it is not practical to attach a chain or cable to such doors in rapid fashion, if at all. Furthermore, in many situations, such as during a combat foot patrol, an available vehicle to perform the pull operation is simply unavailable. 
     Another entry barrier disabling method uses explosives that are placed at the entry barrier&#39;s hardened points, such as the locks and the hinges, such that the explosive detonation disables these points in order to allow easy removal of the door. While effective, this method raises the possibility of collateral damage to both innocents as well as the combatants, which in today&#39;s litigious and 24 hour news cycle society is avoided at all costs. 
     Yet another entry barrier disabling method uses firearms based breaching tools. Essentially, such tools are modified firearms that use a blank firing round which, upon being fired, uses the force from the round&#39;s discharge gases to propel a ram with great force and speed at a target such as a lock, with the ram disabling the target. By using the force of a firearm round, a short pulse extremely violent high force burst is achieved by the ram in order to allow breeching of most defensive obstacles. These devices, which can be found in variety of architectures work with varying degrees of effectiveness, however, certain shortcomings can still be found. 
     One shortcoming is in devices that are pistol based. While a pistol round can expend great energy during discharge, in many hardened targets, such energy falls woefully inadequate to penetrate the defenses of the obstacle being targeted. 
     Many devices require rather extensive setup steps so that while the first use of the device can be achieved with relative ease, being setup well ahead of the breach attempt, if multiple ram impacts with the device are required, which is the case with many hardened entry barriers, subsequent iterations of the device can take time, which time may simply not be available. Many devices overcome this shortcoming by providing a rapid firing of the device so that some of the discharge gases are used to rechamber a round and reset the bolt carrier assembly for subsequent firings of the device. While effective, such devices require some of the energy from the expended round is used for resetting of the device which lessens the impact force of the ram. Additionally, the rapid firing of the device can be a hazard, especially to a novice user, as the percussive forces occasioned by the device can cause an operator to lose control of the device during rapid firing. Furthermore, these devices fail to assure that a live round, as opposed to a blank round, is not accidentally used with the device. A live round fired by these types of devices can cause catastrophic explosive failure of the device possibly resulting in serious injury or death to the operator and these in close proximity to the device. Such live rounds firing are possible with many prior art devices as such device are add-ons to existing firearms so that the firearm is usable both as a breeching tool and as a standard firearm. Carelessness can inadvertently cause such devices to be loaded with a live round when such live round use is strictly undesired. 
     What is needed is a firearm based breaching tool that allows an operator to use the high energy expended during a firearms blank round firing, which tool addresses the above mentioned shortcomings currently found in the art. Specially such a tool must allow an operator to be able to quickly and easily use the tool to ram a breach point and thereafter be able to quickly reset the device for additional ram iterations without having to use some of the energy of the discharged round for the resetting operation. Such a device must be able to use high capacity rounds in order to allow the tool to be used against well hardened obstacles. Such a tool must be relatively safe in operation without the potential for the operator to lose control of the device through repeated ramming iterations caused by inadvertent rapid firing of the device. Such a tool must be able to prevent the accidental use of live rounds within the device. 
     SUMMARY OF THE INVENTION 
     The firearm based breeching tool of the present invention addresses the aforementioned needs in the art by providing a breeching tool that relies on the discharge energy of a high capacity firearm arm round to ram a barrier entry obstacle. The firearm based breeching tool uses all of the energy of the discharged round for the ramming operation, relying on operator energy to reset the device for successive firing. The use of human energy for reset allows for controlled use of the device so that undesired rapid firing of the device is not possible. The firearm based breeching tool uses a familiar firearm architecture so that an operator has immediate comfort in the familiarity of the device so that use of the device is natural, yet the firearm based breeching tool has a hard safety feature that prevents the ability of the device from being loaded with a live round instead of a blank round. Essentially, an assault rifle is mated with a pump action reloading mechanism for cycling new ammunition into the firing chamber once the current ammunition is fired. The pump handle of the shotgun mechanism also resets a piston within the barrel, which piston impacts onto the anvil head of a chisel with the working end of the chisel performing the actual impact onto the target at hand. The use of the pump handle type of reloading and resetting of the device allows all of the energy from the fired ammunition round to be used to accelerate the chisel without needing to scavenge some of the expansion gasses for the reloading operation and also allows the operator of the device to have precise firing control of the unit. 
     The firearm based breeching tool is comprised of an assault rifle lower that has a magazine used to hold rounds of blank ammunition. A firearm upper has a firing chamber and a barrel with a first end proximate the firing chamber and a second open end. The firearm upper is mated with the assault rifle lower. The firearm upper also has a bolt carrier assembly for transporting a blank round of ammunition from the magazine into the firing chamber and expelling a cartridge of the round of ammunition after the ammunition is fired (the cartridge can include an unspent round such as if the round fails to fire or the weapon is cleared). A chisel is slidably disposed within the barrel and extends outwardly from the second end. A piston is slidably disposed within the barrel between the firing chamber and the ram. A pump handle is slidably attached to the outside of the firearm upper and is connected to the bolt via an operating rod. When the device is in a ready position, the chisel and the piston are both located toward the firing chamber. The chisel is held in place by a friction ring encompassing the chisel&#39;s anvil head while the piston is held in place by two small but powerful magnets (such as rare earth permanent magnets). The pump handle is cycled back toward the firing chamber and then forward toward the second end of the barrel thereby transporting a round of ammunition from the magazine and into the firing chamber. This action also resets the trigger assembly of the breeching tool so that when the trigger is pulled, the round of ammunition within the firing chamber fires thereby accelerating the piston onto the chisel causing the chisel to accelerate partially out of the second end of the barrel. A buffer spring assembly prevents the chisel from being expelled out from the second end of the barrel, the buffer spring assembly using a spring to dampen the travel of the chisel. A safety pin is disposed within the firing chamber wherein the pin prevents a live round of ammunition from being properly loaded within the firing chamber. The piston has a protruding pin that is received within a channel, the channel disposed within the barrel, the protruding pin also protrudes outside of the barrel tube. This protruding pin provides a means for the pump handle to reset the piston for the next firing as the pump handle, during its travel back toward firing chamber, catches the protruding pin and thereby moves the piston back toward the firing chamber. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view, partially sectioned, of the firearm based breeching tool of the present invention being used to breech a door. 
         FIG. 2  is an exploded view, partially sectioned, of the firearm based breeching tool. 
         FIG. 3  is a plan view, partially sectioned, of the upper section of the firearm based breeching tool. 
         FIG. 4  is a plan view, partially sectioned, of the bolt carrier assembly and pump of the firearm based breeching tool. 
         FIG. 5A  is a plan view of the chisel used by the firearm based breeching tool. 
         FIG. 5B  is a plan view of an alternate embodiment of the chisel used by the firearm based breeching tool. 
         FIG. 6  is a plan view of the piston used by the firearm based breeching tool. 
         FIGS. 7-10  are plans views, partially sectioned, of the firearm based breeching tool cycling through a firing sequence. 
     
    
    
     Similar reference numerals refer to similar parts throughout the several views of the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, it is seen that the firearm based breeching tool of the present invention, generally denoted by reference numeral  10 , is comprised of a lower receiver  12 , which as illustrated, is a typical lower receiver for an assault rifle such as the illustrated AR-15. The lower receiver  12  has the requisite components of a typical lower receiver that has all of the critical parts and functions for firing a round of an assault rifle lower receiver. While an off-the-shelf assault rifle lower receiver will function correctly, we have modified our lower receiver  12  by removing the stock, recoil spring tube (spring tube hole being capped), recoil spring, and buffer which are not essential for proper functioning of this invention  10 . The lower receiver  12  has a grip  14 , a trigger  16  of standard design, a selector lever  18 , and a modified magazine  20  that receives multiple blank rounds A therein and which is dischargeable from the lower receiver  12  via an appropriate release  22 , a spring and pin ridge  24 , etc. By using a standard lower receiver  12 , an operator, having familiarity with the firearm based breeching tool&#39;s live firing brethren, has immediate familiarity with the device  10 . 
     An upper receiver  26  is removably attached to the lower receiver  12  in the well-known and understood way by aligning tabs  28  on the upper receiver  26  with appropriate receivers (not illustrated) on the lower receiver  12  and pinning the two receivers  12  and  26  together via the aligned apertures  30  on the two units  12  and  26 . The upper receiver  26  is a typical assault rifle upper receiver with a modified barrel. The upper receiver  26  slidably receives a bolt carrier assembly  32  (although a typical bolt carrier will work properly, we have cut ours down so it does not protrude into the area that the recoil spring tube would typically occupy and thus cannot move rearward in order to chamber a round A) that slides within the upper receiver  26  for chambering and firing rounds A. The upper receiver  26  may also have an appropriate rail mount  34  thereon for mounting various accessories onto the device  10  such as a flashlight (not illustrated). Extending outwardly from the main body of the upper receiver  26  is a barrel  36  which has a threaded end  38  and a firing chamber  40 , an expansion passage  42 , and a piston receiver  44 . A piston  46 , encompassed by one or more ribs  48 , is slidably disposed within the barrel  36  in alignment with the firing chamber  40 , the piston  46  having a reset or protruding pin  50  which slides within a slot  52  disposed on the underside of the barrel  36 . A chamber safety pin  54  is positioned within the chamber  40 , so as to physically prevent live ammunition from being used within the device  10 . 
     Attached to the bolt carrier assembly  32  via a operating rod block  56  is an operating rod  58  encompassed by a pump handle spring  60 , the operating rod  58  is attached at its opposing end to a pump handle  62 , the pump handle  62  encircling the barrel  36  and capable of sliding along the barrel  36  back toward the non-barrel end of the upper receiver  26 , the pump handle  62  engaging the protruding pin  50  of the piston  46  when sliding back toward the non-barrel end of the upper receiver  26 . As seen, an upper rail interface  64  and/or a lower rail interface  66  are located on the pump handle  62 . 
     A breeching chisel  68  having an anvil end cap  70 , a shaft  72  and an impact end  74  is slidably disposed within the barrel  36  such that the impact end  74  is located externally of the barrel  36 . As seen in  FIGS. 5A and 5B , the impact end  74  may be a large footprint impact end ( FIG. 5A ) or a small footprint impact end ( FIG. 5B ) depending on the needs of the job at hand. 
     A buffer spring assembly  76  is threadably attached to the end of the barrel  36 , the buffer spring assembly  76  having a main body  78  that threadably attaches to the barrel  36  through which the chisel  68  passes. A dye spring retainer  80  is seated within a proximal end of the main body  78  and seats within the end of the barrel  36 . The chisel  68  also passes through the dye spring retainer  80 . A spring  82  is disposed within the main body  78  and is retained within the main body  78  via an end cap  84  that is threadably attached to the distal end of the main body  78 . The spring  82  decelerates the chisel  68  during firing of the device  10  so as to prevent the chisel  68  from being blown out of the end of the barrel  36 . 
     In assembly, the upper receiver  26  is attached to the lower receiver  12  and secured as appropriate. The piston  46  is positioned within the barrel  36 . The chisel  68  is positioned within the barrel  36  and the buffer spring assembly  76  is threadably attached to the end of the barrel  36  with the chisel  68  passing there and through the spring  82  of the buffer spring assembly  76 . A friction ring spring  86  encompasses the anvil head  70  of the chisel  68  and holds the chisel  68  in its set ready position within the barrel  36 . The magazine  20  is loaded with rounds of blank ammunition A appropriate for the firearm at issue. A round A is chambered by sliding the pump handle  62  back toward the non-barrel end of the upper receiver  26 , similar to loading a pump action shotgun. Sliding of the pump handle  62  causes the piston  46  to be slid toward and into the piston receiver  44  where at the piston  46  is held in the ready position by a pair of piston receiver magnets  88 . The sliding of the pump handle  62  also causes a round A to be chambered into the firing chamber  40  of the upper receiver  26 , which chambering also causes the trigger assembly to be placed into a firing position as is typical of such firearms. Essentially, the device  10  is manually reloaded via pump action pumping so that the device  10  is reloaded like a shotgun. As a blank round of ammunition A is shorter than a live round of the same caliber of ammunition, the chamber safety pin  54  is positioned so as to physically prevent a live round from fitting properly within the firing chamber  40  and thereby prevents a live round from being properly chambered within the device  10  so that if a person inadvertently loads the magazine  20  with live rounds, the chamber safety pin  54  prevents such a round from being chambered and fired. Once the blank round A is properly chambered and the pump handle  62  is returned to its ready position, the device  10  is ready for firing. In this position, the chisel  68  is positioned such that the friction ring  86  encompassing the anvil head  70  holds the chisel  68  in its placed position within the barrel  36  with the anvil head  70  positioned medially within the barrel  36 . Once the round A is fired in the usual way, the gas expended by the round A passes through the expansion passage  42  and onto the piston  46 . The expanding gas rapidly accelerates the piston  46  through the barrel  36  until the piston  46  impacts the anvil head  70  of the chisel  68 , thereby rapidly accelerating the chisel  68  with the impact end  74  performing work such as penetrating a hardened door D. The buffer spring assembly  76  prevents the piston  46  from further travel toward the end of the barrel  36  while the end cap  84  prevents the chisel  68  from being expelled from the device  10 . The spring  82  absorbs any excess forces on the chisel  68  in order to prevent the chisel  68  from being blown out of the end of the barrel  36 . Porting (not illustrated) within the barrel  36  relieves any excess pressure within the barrel  36  whenever the piston  46  travels forward toward the chisel anvil  70 , the proximal end of the piston  46  clears the slot  52  allowing any excess gas to escape through the slot  52  and be trapped within the pump handle  62 . 
     If another iteration of the device  10  is needed, for example, multiple hinges must be breached, the pump handle  62  is pumped back and forth through another cycle thereby chambering another round A, resetting the piston  46  and the trigger mechanism, expelling the spent cartridge, reloading a new round A from the magazine  20 , and readying the device  10  for another firing. Multiple iterations can be performed as needed. If additional rounds A are needed, the magazine  20  is removed from the lower receiver  12 , replenished or replaced with a stocked magazine  20 , and the device  10  continues use as desired. 
     While the invention has been particularly shown and described with reference to an embodiment thereof, it will be appreciated by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the invention.