US 20020170551 A1
A compressed gas powered gun includes an electronic actuator to achieve greater efficiency in the operation of the gun. In one aspect, the gun is operable in either a manually operating mode or an electronically operating mode.
1. An electronically actuating compressed gas firing system operable in a first mode to discharge a projectile from a barrel of a gun or the like and a second mode to reload the gun, the firing system being powered by a compressed gas source which provides compressed gas at an inlet, the firing system comprising:
a firing chamber disposed to receive compressed gas from the compressed gas source for supplying compressed gas to expel the projectile through the barrel when the firing system is in the first mode;
a flow valve disposed between the inlet and the firing chamber, the flow valve being movable between an open position in the first mode of the firing system wherein compressed gas is permitted to flow from the compressed gas source to the firing chamber and a closed position in the second mode of the firing system wherein the firing chamber is isolated from the gas source so as to maintain a preselected pressure in the firing chamber;
a bolt assembly operable to seal the firing chamber when the firing system is in the second mode and to direct compressed gas discharged from the firing chamber toward the projectile when the firing system is in the first mode;
an electronic actuator; and
an electronic control circuit operable to provide control signals to the electronic actuator, thereby operatively releasing the bolt assembly when the firing system is in the second mode.
2. The firing system of
3. The firing system of
4. The firing system of
5. The firing system of
6. The firing system of
7. A paintball gun including a firing system being powered by a compressed gas source comprising:
a manual triggering mechanism with a first linkage for actuating the firing system in a first operating mode;
an electronic actuating mechanism with a second linkage for actuating the firing system in a second operating mode; and
a change-over mechanism for selectively coupling a trigger to either the manual triggering mechanism or the electronic actuating mechanism.
8. The paintball gun of
9. An electronically actuating trigger mechanism for a weapon being actuatable between a firing mode to fire the weapon and a ready-to-fire mode to place the weapon in condition for firing, comprising:
a switching mechanism in operable relation with a trigger;
an actuator being operable to place the weapon in the firing mode or the ready-to-fire mode; and
a control circuit operable to supply control signals to said actuator.
 This is a continuation-in-part of U.S. application Ser. No. 60/103,171, filed Oct. 6, 1998, the subject matter of which is incorporated by reference in its entirety. This application is also related to U.S. patent application Ser. No. 08/955,047, filed Oct. 21, 1999, now U.S. Pat. No. 5,913,303, issued Jun. 22, 1999, and U.S. patent application Ser. No. 08/955,187, filed Oct. 21, 1997, the subject matter of which is also incorporated by reference in their entirety.
 This invention generally relates to an electronic actuator coupled with a trigger mechanism for use in compressed gas powered weaponry or the like.
 A variety of different types of weaponry which utilize discharged compressed gas to fire projectiles are known. These compressed gas powered weapons have particular use in a variety of applications including tranquilizer guns and pellet marking guns which are sometimes referred to as “paintball guns.” Generally marking guns use compressed gas to fire a relatively fragile projectile which comprises a frangible shell which is filled with a marking composition. The capsules are designed to break upon impact with a target and thereby discharge the marking material onto the target.
 Such marking guns have a variety of different uses. For example, they may be employed to segregate livestock within a herd, assist in the counting of wild animals or for training of military or law enforcement personnel through simulation exercises. Likewise, they may be used by military and law enforcement personnel for crowd control. Another very popular use for such marking guns is for recreation. In particular, paintball marking guns are used for “war games” in which participants attempt to hit other combatants with paintballs thereby marking them and eliminating them from the game.
 One attribute which is extremely important to users of paintball marking guns which are intended for such recreational war games, as well as those used for other purposes, is the manner in which the gun is fired. Obviously, paintball marking guns which are capable of increased firing rates offer the user a significant competitive advantage over his/her fellow combatants. One significant factor which influences the firing rate of any weapon is the type of firing arrangement that is employed. Paintball marking guns typically may employ manual, semi-automatic and fully automatic firing arrangements. A manual firing arrangement requires appropriate manipulation of the gun before successive projectiles are fired. In contrast, a semi-automatic firing arrangement enables a projectile to fired each time the trigger is depressed, while an automatic firing arrangement will fire multiple projectiles each time the trigger is pulled.
 Although fully automatic weapons may seem desirable, they suffer from various shortcomings. For example, they consume increased amounts of both ammunition and compressed air and have proven problematic, particularly due to feeding mechanism failure. Moreover, they have not achieved widespread success due to regulation prohibiting their use in many recreational settings.
 Accordingly, in view of the foregoing, it is a general object of the present invention to provide a trigger mechanism for a weapon which overcomes the deficiencies of the prior art.
 Another object of the present invention is to provide a trigger mechanism for compressed gas powered weapons which provides excellent performance and is very easy to maintain.
 It is a more particular object of the present invention to provide a compressed gas powered weapon that utilizes an electronically actuated firing mechanism.
 These and other features and advantages of the invention will be more readily apparent upon reading the following description of a preferred exemplified embodiment of the invention and upon reference to the accompanying drawings wherein:
FIG. 1 is a side view of a compressed gas powered gun that utilizes the teachings of the present invention;
FIG. 2 is a partial side sectional view of the compressed gas powered gun of FIG. 1, taken axially through the gun, showing the firing system in a ready-to-fire mode;
FIG. 3 is a partial side sectional view of the compressed gas powered gun showing the firing system in a firing mode prior to release of an actuating bolt assembly;
FIG. 4 is an electrical block diagram illustrating control circuitry used in the electronic actuating system according to one embodiment of the present invention; and
FIG. 5 is an electrical block diagram illustrating control circuitry according to a second embodiment of the present invention.
 While the invention will be described and disclosed in connection with certain preferred embodiments and procedures, it is not intended to limit the invention to those specific embodiments. Rather it is intended to cover all such alternative embodiments and modifications as fall within the spirit and scope of the invention.
 Generally, the present invention relates to an electronic actuating system for a compressed gas powered weapon or the like which is capable of being operated with greater efficiency as compared to known firing systems. Such efficiency is achieved through a novel trigger mechanism and control and actuating circuitry which is incorporated into the firing system of the present invention. In one embodiment, the trigger mechanism is operable in either a mechanical mode or an electronically actuating mode to assist the user in successively actuating the trigger.
 While the present invention is described in connection with a compressed gas powered gun, which has particular use a paintball marking gun, it will be readily appreciated that the teachings of the present invention can also be applied in other contexts. These include, for example, other types of compressed gas powered weapons. However, it should be understood that the actuating and switch-over mechanism of the present invention may be utilized in many applications other than compressed gas powered weapons.
 FIGS. 1-3 illustrate one preferred embodiment of a compressed gas powered gun which incorporates the firing system of the present invention. Certain details of the gun are also disclosed in U.S. Pat. No. 5,280,778, which is incorporated herein by reference in its entirety. As best shown in FIG. 1, the gun 10 comprises a longitudinally extending frame support or rail 12 with a trigger-guard 14 and handle 16 depending therefrom. A pivotally mounted trigger 18, the operation of which is described in more detail below, is disposed within the trigger-guard 14.
 The firing system is operable in a firing mode wherein a projectile is expelled from the gun and a ready-to-fire or reloading mode which places the gun in condition for firing. As seen in FIG. 2, a projectile 20, such as a marking pellet or paintball, exits an elongate, generally cylindrical barrel 22 in the direction of arrow 24 during the firing mode. An ammunition feeding tube 26 (FIG. 1) is disposed to supply a plurality of projectiles to the gun, one at a time, as will be understood by those skilled in the art.
 For providing connection of the gun to a source of compressed gas, the gun includes an inlet port 30 which in the preferred embodiment comprises a conventional adapter which allows an air line or hose (not shown) to be quickly and easily connected and disconnected from the gun. The source of the compressed gas preferably comprises a tank of compressed air (not shown) as will be understood by those skilled in the art. In order to provide for ease of movement, the compressed air tank may be strapped to the back of the user or carried on a belt. The compressed gas source preferably is supplied at a pressure of approximately 700 pounds per square inch (psi). Of course, it should be appreciated that different types of sources of compressed gas could be used with the present invention. In addition, while compressed air is preferred, other compressed gases such as nitrogen may be used.
 The compressed gas or air passes from the inlet port 30 via an annular inlet passageway which, in the illustrated embodiment, extends along the rail of the frame 12. This inlet passageway provides a passageway to a compressed gas delivery system which operates to control and meter the compressed gas received from the compressed gas source in both the firing and ready-to-fire modes of the firing system. Specifically, the compressed gas delivery system includes a pressure regulating system or assembly 34 and a fluid pathway which interconnects the compressed gas inlet port with an air or firing chamber 36.
 In accordance with one preferred embodiment of the present invention, a pressure regulating assembly is adapted to rapidly recharge the firing chamber after it is expelled by filling at an increased pressure until a preselected pressure is attained. In the illustrated embodiment, the pressure regulating assembly 34 is adapted to operate at a very high speed and provide for full pressure recharge of the firing chamber 36. This results in the firing chamber 36 being charged with compressed gas to the preselected pressure very rapidly thereby increasing the potential firing rate of the gun 10.
 The pressure regulating assembly 34 and the fluid pathway are disposed in a cylindrical terminal housing or valve body section 38 of the gun. The regulating assembly 34 generally comprises a screw-type control and valve arrangement including a valve 40 disposed in the fluid pathway interconnecting the inlet port 30 and the firing chamber 36 and a regulator piston subassembly 42. The main structural details of the valve 40 include a head portion 44, a valve stem 46, a seat 48 and a biasing spring 50. A generally cylindrical regulator valve chamber 52 is formed in the valve body section 38 of the gun which is in fluid communication with the inlet passageway 32 via a fluid passageway 54 provided in the field strip screw 55. The valve head 44 is contained within the regulator valve chamber 52 while one end of the stem portion 46 extends outwardly to the regulator piston subassembly 42.
 The valve 40 is operable to move between an open position, wherein compressed gas flows from the inlet port 30 to the firing chamber 36 via the fluid pathway and a closed position, wherein the inlet port 30 is isolated from the firing chamber 36. Specifically, when the valve 40 is in the closed position, the valve head 44 engages the valve seat 48 to thereby close off the flow of compressed gas to the firing chamber 36 as shown in FIG. 3. When the valve 40 is in the open position, compressed gas flows between the outer periphery of the valve head 44 and the walls of the regulator valve chamber 52 as shown in FIG. 2. The flow of compressed gas past the valve 40 continues to an on/off flow valve chamber 56 via a fluid passageway 58. In turn, the flow valve chamber 56 is interconnected with the firing chamber 36 by way of a second fluid passageway 60 which completes the fluid pathway between the inlet port 30 and the firing chamber 36.
 In order to control the pressure in the firing chamber 36, the regulator piston subassembly 42 is adapted to move the valve 40 to a closed position when a predetermined pressure of compressed gas is sensed and to urge the valve 40 to an open position when a pressure less than the preselected pressure is sensed. The regulator piston subassembly 42 is arranged in a regulator piston bore 62 which is sealed from the flow of gas from the regulator valve chamber 52. In order to prevent gas from leaking into the regulator piston bore, around the valve stem an o-ring seal 64 is provided. The main structural components of the regulator piston subassembly include a threaded adjusting nut 66, a biasing spring 68 and a regulator piston 70.
 In the preferred embodiment, a blow off valve arrangement valve is provided which includes a head 67 and biasing spring 69. When an over-pressure condition is sensed, the valve permits the compressed to vent to atmosphere via an overflow port 73.
 In order to sense the pressure of the gas in the firing chamber 36, the regulating assembly 34 further includes a sensing line 72. The sensing line 72 is in fluid communication with the regulator piston bore 62 and is adapted to apply the pressure of the gas in the firing chamber 36 to the regulator piston subassembly 42. In a preferred embodiment, the forward end of the valve stem 46 extends to a location adjacent the firing chamber 36 and the sensing line 72 comprises a bore in the valve stem 46 which extends from adjacent the firing chamber 36 to the regulator piston bore 62 as shown in FIGS. 2-3.
 When the firing chamber 36 is being filled or charged with compressed gas during the ready-to-fire mode of the firing system, the regulating springs 68, 69 bias the regulator piston 70 toward a forward position in the piston bore 62, which in turn, acts to move the valve head 44 away from the valve seat 48 as best shown in FIG. 2. The regulator piston 70 remains in this forward position and thereby prevents the valve 40 from closing until a predetermined pressure is supplied to the firing chamber 36 and to the piston bore 62 via the sensing line 72. When the pressure in the firing chamber 36 and the piston bore 62 reach the predetermined pressure, as shown in FIG. 3, the regulator piston 70 is moved counter to the force of the regulator springs 68, 69 to a rearward position which causes the valve 40 to engage the valve seat 48 and seal the regulator valve chamber 52. The compressed gas in the portion of the fluid pathway upstream from the valve head 44 and the biasing spring 50 coact to maintain a closure tension on the valve 40.
 When the pressure in the air chamber 36 and, in turn, in the regulator piston bore once again falls below the predetermined pressure such as after a firing sequence, the regulating piston subassembly 42 urges the valve 40 to an open position. Compressed gas supplied to the regulator piston bore 62 via the sensing line 72 thereafter acts against the tension of the regulating springs 68, 69 to move the piston 70 rearward. Thus, compressed gas is again discharged until the pressure in the air chamber 36 reaches the predetermined level sufficient to urge the valve 40 closed.
 In contrast to conventional arrangements in which the compressed gas is regulated to a lower pressure as soon as it enters the gun or the compressed gas delivery system, the described embodiment “regulates” the pressure in the firing chamber 36 itself by shutting of the supply of compressed gas when the firing chamber 36 reaches the desired pressure. Thus, the regulating system allows the firing chamber 36 to charge at very nearly the full line pressure of the compressed gas source. As can be appreciated, this allows the firing chamber to fill with compressed gas to the desired pressure much more rapidly than conventional designs.
 This arrangement also ensures precise operation of the gun 10 for successive firings over a wide range of ambient temperatures. For example, when the ambient temperature increases, thereby increasing the gas pressure in firing chamber 36 and the piston bore 62, the regulator piston 70 is urged rearward to close the valve 40. If the ambient temperature increases to a level where the pressure in the piston bore 62 exceeds the desired firing chamber pressure and the gas supply pressure by a sufficient amount, i.e., 650 p.s.i., the overflow valve will move sufficiently rearwardly to permit venting through the port 73. Conversely, when the ambient temperature decreases, thereby decreasing the pressure in the firing chamber 36 and the piston bore 62, the gas supply pressure decreases, urging the valve 40 to an open position. In this way, the pressure regulating assembly 34 operates to maintain a desired pressure supplied to the air chamber 36 for each firing of the gun.
 In order to allow for the adjustment of the pressure to which the firing chamber 36 is charged, and thereby the velocity of the projectile 20, means are provided for adjusting the pressure at which the regulator valve 40 closes. Specifically, in the illustrated embodiment, the amount of force exerted by the first regulating spring 68 on the regulating piston 70 can be controlled through manual adjustment of a threaded velocity nut 66 provided on the end of the valve body 38. For example, in order to increase the pressure to which the firing chamber 36 is charged, the velocity nut 66 is turned so as to increase the force that the first regulating spring 68 applies to the regulating piston 70. A relatively higher pressure will then be required to urge the regulating piston 70 rearward and thereby close the valve 40. In a preferred embodiment, the pressure regulating assembly 34 should be set to shut off the flow of compressed gas from the inlet port 30 when the pressure in the air chamber 36 reaches approximately 450 psi.
 In order to protect against an over pressure condition in the compressed gas delivery system resulting from a seal failure or the disassembly of the gun when the firing system is under pressure, the blow off valve and over pressure vent 73, discussed above, may also be provided.
 In order to ensure that the preselected pressure is maintained in the firing chamber 36 for the firing mode, the firing system further includes a on/off valve 74 which seals off the firing chamber 36 from the compressed gas source when the firing system is operating in the firing mode. The on/off flow valve 74 is movable between open and closed positions and, in particular, is operable to open and thereby permit fluid communication between the firing chamber 36 and the inlet port 30 in the ready-to-fire mode of operation, as shown in FIG. 2. This enables the firing chamber 36 to be charged with compressed gas to the predetermined pressure via the compressed gas delivery system during the ready-to-fire mode. In the firing mode of operation, the on/off flow valve 74 closes thereby isolating the firing chamber 36 from the inlet port 30 and the compressed gas source. This isolation of the firing chamber 36 from the compressed gas source prevents compressed gas from flowing into the firing chamber to replace the air which has been discharged from the firing chamber in order to expel the projectile. This is of particular importance because the pressure in the regulator piston bore 62 has dropped resulting in the opening of the regulator valve 40. The on/off flow valve 74 is movable transversely relative to the longitudinal axis of the gun between the open and closed positions. In order to prevent compressed gas from leaking past the on/off flow valve when it is in the closed position, an o-ring seal 78 is provided adjacent the upper end of the flow valve chamber 56. In addition, a second o-ring seal 79 is provided adjacent the lower end of the flow valve chamber to prevent compressed gas from leaking out of the compressed gas delivery system.
 The air or firing chamber 36 supplies the compressed gas that expels the projectile through the barrel 22 when the firing system is in the firing mode. The air chamber 36 is defined by a bore formed in the main body portion of the gun 10 terminating at one end with an intermediate firing tube or power tube 80. An annular sleeve 82 interfits within the power tube 80 and, along with the power tube 80, defines a discharge path for compressed air contained in the firing chamber 36 to blast into a breech 84 of the gun 10. The annular sleeve 82 includes a tapered portion 86 that further defines a passage for the blast of compressed gas. This tapered portion 86 on the power tube 80 is configured such that the air flows out of the air chamber 36 and the power tube at a controlled rate which prevents relatively fragile projectiles such as paintballs from breaking as a result of too much pressure building up behind the paintball. Inasmuch as the pressure supplied to the firing chamber 36 has been substantially reduced from the maximum available pressure from the compressed gas source, the volume defined by the firing chamber 36 is substantially larger than found in many known arrangements.
 The blast of compressed gas exits the air chamber 52 upon actuation of a bolt assembly 88 which includes a power piston 90. The power piston 90 comprises head and body sections 91 and 92, respectively, with the body section 92 being sized to fit within the annular sleeve 82 and power tube 80. FIG. 2 also illustrates the remaining structural features of the bolt assembly 88, including a cylindrical actuating bolt 94 disposed in surrounding relation to the annular sleeve 82 and power tube 80. The actuating bolt 94 includes a protruding dog portion 95 disposed at one of its ends. A recoil spring 96 retracts the actuating bolt 94 against a bumper 97 when the actuating bolt 94 is returned to a ready-to-fire position.
 In accordance with the invention, an electronic actuating assembly is provided to permit precise operation of the gun. In addition, control circuitry is provided which generates appropriate signals to control the rate of fire, the number of shots fired per trigger pull, and present a fully automatic mode of operation to the user.
 In keeping with the invention, the bolt assembly 88 is maintained in a ready-to-fire position with the use of a trigger mechanism which includes a sear 98 having an arm 99 that is rotatable about a pivot 100, which in a preferred embodiment comprises a threaded roller bearing axle. The arm 99 has a transversely extending actuating member 102 at one end, located on one side of a pivot 100, and an interlocking element 104 at the other end, located on the other side of the pivot 100. The actuating member 102 is generally aligned with the on/off flow valve 74. The interlocking element 104 includes a notched portion that engages the dog portion 95 of the actuating bolt 94 in the ready-to-fire position. The interlocking element 104 preferably also includes an elongated section extending substantially along the path of travel of the actuating bolt assembly 88 to provide a stop surface that prevents the actuating bolt assembly from engaging the interlocking element 104 during recoil of the actuating bolt assembly.
 A first manual actuating lever 106 projects transversely on the side of the latch arm 99 opposite the actuating member 102 and the interlocking element 104. A sliding trigger arm 108 disposed within the handle 16 operates to transmit force from the trigger 18 to the actuating lever 106. As explained in detail in said U.S. Pat. No. 5,280,778, this provides for semi-automatic firing of the gun 10 in operation. In the illustrated embodiment, the trigger arm 108 comprises a first link 110 which is pivotally connected to the manual actuating lever 106 and a second link 112 which is threaded into the first link. With this arrangement, any play in the trigger mechanism can be selectively adjusted merely by turning the second link 112 relative to the first link 110 and thereby thread the second link further out of or in to the first link.
 For permitting electronic actuation of the gun, the sear 98 comprises a second electronic actuating lever 114 which extends outwardly from the pivot 100. The second actuating lever 114 is angularly offset from the first actuating lever 106. A push rod 116 is operably connected with a solenoid 118 disposed in the handle of the gun. The push rod 116 operates to transmit force to the second actuating lever 114 when the solenoid is energized. This action rotates the sear 98 to release the bolt assembly.
 In accordance with one aspect of the invention, a switch-over mechanism is provided for permitting selection between a manually operable mode and an electronically actuating mode. As shown in FIGS. 2 and 3, the trigger 18 comprises a finger-engageable portion 18 a, disposed on one side of a trigger axis of rotation 18 b. The trigger further includes an outwardly protruding arm 18 c, disposed opposite the finger-engageable portion 18 a and the trigger axis 18 b. The switch-over mechanism in this embodiment is a movable selector lever 19 that coacts with the trigger arm 18 c. The lever 19 includes a camming surface 19 a disposed to selectively couple the trigger arm with the electrical contacts of a trigger switch 150. When oriented in the position shown in FIGS. 2 and 3, the switch-over mechanism permits the trigger arm 18 c to close the contacts of the electronic trigger switch 150. On the other hand, when rotated such that the camming surface 19 a is disposed in contacting relation with the trigger arm 18 c, the travel of arm 18 c is restricted to effectively prevent the arm from urging the trigger switch contacts in closed relation. Optionally, the selector lever 19 is movable to a safe position to effectively prevent the trigger from being pulled.
 The switch-over mechanism thus permits a user to readily manually select either a manual operating mode or an electronic operating mode. This feature is particularly advantageous when, for example, the user encounters a malfunction in one operating mode, such as would be the case with electronic circuit malfunction or power supply failure.
FIG. 4 illustrates a block circuit diagram for control circuitry that may be utilized in conjunction with the electronic mode of operation. Generally, the control circuitry is operable to provide a single pulse of a particular duration, or alternatively, a series or “burst” of pulses, each having a selected duration to a solenoid 118. In this fashion, the control circuitry provides various modes of operation, while at the same time, a precise degree of control of movement of the sear 98. In the illustrated embodiment, the control circuitry is operable to provide single shot pulses between approximately 10 milliseconds and 70 milliseconds. These pulses, in turn, energize the solenoid coil L1. The solenoid coil L1 operates in conjunction with an armature winding as would be understood by those skilled in the art to actuate the arm 114. This action, in turn, rotates the sear 98 in order to release the bolt assembly and fire the gun.
 As shown in FIG. 4, a voltage source, which in this case is 18 volts, is coupled through a main power switch 200, which is manually operable by the user to permit use of the electronic circuitry (see FIG. 1). The power supply may be located in the trigger guard, as shown by the battery-receiving portions 152 and 154 in FIG. 3. Similarly, the control circuitry may be located on a circuit board 156, disposed in the handle 16 of the gun.
 The voltage supplied by the power source is sufficient to energize the solenoid coil L1. However, this voltage is reduced through a zener diode D1 to approximately 14.4 volts so that it may be used to provide power to the control circuitry of the system. A resistor R1 is coupled between the zener diode D1 and ground.
 When the gun is operable in the electronic actuating mode as described above, depression of the trigger closes the trigger switch contacts 150. Closure of the trigger switch 150 causes a capacitor C1 to begin charging through a resistor R3. The increased voltage is applied to the input of a Schmidt trigger implemented as a nand gate 204. Based on the time constant of the RC network of C1 and R3, the output of Schmidt trigger 204 is a negative pulse having a duration of approximately 1 millisecond. Eventually, the capacitor C1 becomes fully charged such that the current through R3, and resultant voltage applied to gate 204 is zero.
 The output of the gate 204 is applied to the trigger input of a timer integrated circuit IC1 in order to provide a control signal at the output (pin 3 of IC1). The duration of the output control pulse determined by an RC time constant applied to the threshold input of the timer circuit IC1, in this case a potentiometer R5 and a capacitor C4. In the preferred embodiment, the threshold of timer circuit IC1 is adjustable between 10 milliseconds and 70 milliseconds based on the adjustment of potentiometer R5. The resultant output control signal is provided at the output terminal of timer circuit IC1. This output pulse is passed through a limiting resistor R5 to the gate of a switching transistor, denoted as MOSFET Q1. When the output signal is applied to the gate of Q1, current is drawn through the solenoid coil, denoted as inductor L1. As described above, this causes the arm 116 to move and release the bolt assembly.
 When the trigger is released, the trigger switch contacts 150 are opened. This causes the capacitor C1 to discharge through a resistor R2 to reset the timer circuit IC1. Similarly, capacitor C4 discharges through the discharge input of the timer circuit.
 The following Table 1 provides a summary of the components utilized in one preferred implementation of the control circuit shown in FIG. 4:
FIG. 5 illustrates an alternative embodiment for controlling the electronic actuator. In this alternative embodiment, the power source is supplied to a voltage regulator integrated circuit IC1. The output of voltage regulator circuit IC1 provides a reduced voltage signal at a node 204. The circuit further includes a two-position DIP switch matrix 206. Based on the settings of the dip switches of switch matrix 206, various functionality may be achieved, as described below. The output of switch matrix 206 is provided to inputs of a micro controller IC2. For example, the following dip switch settings may correspond with the described functionality:
 The micro-controller operates in a logical fashion based on the switch settings to provide an output control signal or signals, having a desired duration. This output control signal is provided through resistor R4 to the gate terminal of a MOSFET transistor Q1. The drain terminal of transistor Q1 is connected to one of the terminals of the solenoid coil. In this manner, a control signal is applied to precisely switch the solenoid on and off at the desired times.
 The following Table 2 provides a summary of the components used in the implementation shown in FIG. 5:
 Of course, the microcontroller may be programmed to provide additional functionality as well.
 In accordance with an optional feature of the invention, the trigger mechanism may be configured such that a user's finger is “pushed back” after the gun 10 is fired through the execution of a pull stroke of the trigger 18. This provides the sensation of a “reactive trigger.” The pushing back of the finger after the trigger 18 is actuated or pulled to fire the gun 10 helps the user pull the trigger in more rapid succession, thereby helping the user to achieve an increased firing rate. The trigger mechanism is operable to actuate the firing system from the ready-to-fire mode to the firing mode to fire the gun upon the execution of a pull stroke of the trigger 18 and from the firing mode back to the ready-to-fire mode to place the gun back in condition for firing upon the execution of a return stroke of the trigger 18. The pushing back of the user's finger after the gun is fired is accomplished by increasing the force applied through the trigger mechanism on the trigger 18, and counter to which the trigger must be pulled to fire the gun, immediately after the gun is fired. Since a lesser force is necessary to pull the trigger 18, this increase in the force opposing the trigger pull has a tendency to force the trigger 18 through the return stroke even if the user has not sufficiently released the trigger. Once the gun 10 is urged back in condition for another firing sequence, the force applied on the trigger 18 through the trigger mechanism is reduced in order to enable the trigger to be manually pulled with greater ease.
 In the illustrated embodiment of the invention, an increased force applied on the trigger after the gun is fired is accomplished by configuring the on/off flow valve 74 with a differential piston head 120. The differential head 120 of the flow valve comprises a first portion 122 with a relatively larger effective surface area and a second portion 124 with a relatively smaller surface area. Thus, when the flow valve 74 is open, the system relies on the second portion 124 of the differential piston since as the effective area to which the pressure is applied. This results in a relatively smaller force being applied to the on/off flow valve 74 by the compressed gas in the system when the flow valve is moving to the closed position as compared to the force applied on the on/off flow valve 74 as it moves to the open position. As the differential piston head 114 is moved toward the O-ring seal 78, the system relies on the force applied to the lesser diameter portion 118 to provide resistance to the trigger pull.
 On the other hand, when the air chamber has expelled and the differential piston head 120 is in engagement with the upper O-ring seal 78, the force applied to the system is transferred to the larger first portion 122 of the piston head 120. At this point, the gas from flow chamber beneath the head 120 has expelled. Likewise, the regulator valve 40 opens and the system upstream from the on-off valve goes to the full line pressure of the compressed gas source. This slams the on-off valve back to the open position with greater force than applied to the valve when moved from the open position to the closed position. Once returned to the open position, i.e., when the larger diameter head 114 is disengaged from the O-ring seal 78, the effective area of the on-off valve upon which the pressure acts is once again the smaller diameter piston head 122.
 Specifically, as the first step of the firing sequence, the trigger 18 is pulled and the resultant longitudinal movement of the trigger arm 108 acts to rotate the actuating lever element 106 of the sear in a clockwise direction (relative to FIGS. 2-6) which in turn rotates the sear arm 99 in the clockwise direction. As shown in FIG. 4, the rotation of the sear arm 99 forces the on/off flow valve 74 into the closed position in response to the movement of the actuating member 102. This movement of the flow valve 74 into the closed position is resisted by the downward force (relative to FIGS. 2-6) exerted on smaller second portion 118 of the differential piston head on the flow valve 74 by the compressed gas in the system.
 As shown in FIG. 3, once the on/off flow valve 74 has closed, the interlocking element 104 on the sear 98 releases the dog portion 95 of the actuating bolt and the compressed gas in the firing chamber 36 moves the power piston 90 rapidly forward and is released from the power tube 80 resulting in the discharge of the projectile 20 from the barrel 22. Upon the release of the compressed gas in the firing chamber 36, the compressed gas in the regulator piston bore 62 is also released via the sensing line 72 resulting in movement of the regulator valve 40 back into the open position. After the gun 10 has been fired, the gas pressure maintained in the system upstream from the on/off flow valve 74 continues to exert a downward force on the on/off flow valve. However, since all of the compressed gas downstream from the on/off flow valve 74 has been discharged, the effective area on which it acts is the larger first portion of the differential piston head. Thus, the force acting on the flow valve 74, and in turn on the trigger 18 through the sear 98, is increased immediately after the compressed gas is discharged from the firing chamber 36. Since the force now applied on the trigger 18 is greater than the force that had to be overcome to pull the trigger (or to overcome the force applied by the actuator), this force tends to force a user to release the trigger 18 and allow the firing system to return to the ready-to-fire mode. In one preferred embodiment, it takes approximately 4 lbs. to pull the trigger and as soon as the gun is fired the force increases to 8 lbs. It has been found that this “reactive trigger” can enable a user to increase his or her firing rate by approximately thirty-three percent over conventional trigger arrangements.
 In addition, upon the release of the compressed gas in the firing chamber 36, the recoil spring 96 drives the actuating bolt 94 rearwardly against the bumper 97 where it is held in place by the force of the recoil spring. The increased downward force exerted on the on/off flow valve 74 will force the trigger 18 through the return stroke. In particular, the force on the on/off flow valve 74 moves the actuating member 102 of the sear to effect slight counterclockwise rotation of the sear 98 to both open the on/off flow valve 74 and to latch the actuating bolt 94 with the interlocking element 104. The firing chamber is then recharged to the desired pressure via the compressed gas delivery system as described above.
 The differential between the force applied on the trigger 18 during the pull stoke and the force applied during the return stroke is further accentuated by the regulating system of the present invention.
 Particularly, as soon as the regulator valve 40 reopens because of the discharge of gas from the firing chamber 36, the pressure in the portion of the compressed gas delivery system upstream from the on/off flow valve 74 increases from the regulated pressure to the full line pressure of the compressed gas source. This increase in the pressure results in a greater downward force being applied to the on/off flow valve 74.
 Various modifications may be implemented as well. For example, the electronic actuator may be replaced by an electro-pneumatic actuator, such as a solenoid valve and a ram push arm arrangement. In this case, the solenoid valve is operable to open a pneumatic chamber to thereby permit a quantity of compressed gas to enter the pneumatic ram. Those skilled in the art will appreciate that the movement of the ram may be operable to either extend or retract to actuate the sear. Alternatively, an additional solenoid may be provided to provide precise control of compressed air supplied to the on-off valve or other components of the gun.
 In accordance with another optional feature of the invention, the electronics and other appropriate components may be provided as a kit that is used to “retire-fit” existing paintball guns configured to operate in a manual mode alone. That is, one or more of the described components, i.e., the modified sear 98, solenoid and actuating arm subassembly, circuit board 156 and/or modified trigger guard 14, may be utilized to retire-fit such existing weapons.
 While this invention has been described with an emphasis upon preferred embodiments, it will be obvious to those of ordinary skill in the art that variations of the preferred embodiments may be used and that it is intended that the invention may be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications encompassed within the spirit and the scope of the invention as defined by the following claims.