The term firing assembly generally refers to the bolt and other firing components used in the marker. The Shocker Sport uses a unique dual-solenoid operation that requires two separate assemblies to work in tandem (bolt and firing piston). There's a third major section called the fill poppet which assists the firing of the marker.
This is a quick synopsis of the firing cycle. The fire piston is activated using the 3000 "fire" solenoid, which closes the dump chamber as well as fires the ball. After the fire piston closes, the bolt piston is activated using the 4000 "bolt" solenoid, loading a new ball the closing the chamber afterward. After this occurs, the marker is ready to fire once again. A detailed animation is provided below, both fast and slow.
Fire Piston:
The fire piston is located at the front of the marker and consists of a housing component inside which the actual "fire piston" slides. While closed, the fire piston seals off the marker's dump chamber, which is where pressure is stored before being released to fire the ball. The piston's housing is ported to allow pressure into the front, which pushes and holds the fire piston closed, sealing the chamber.
During firing, the 3000 "fire" solenoid applies air pressure to the back of the fire piston, which increases the force on that side, and pushes it forward. When this happens the dump chamber seal is unseated and it allows the pressure inside the chamber to be released. The air travels through the front of the housing and up through the bolt, then down the barrel to fire the ball.
· The fire piston is fitted with a delrin ring (called the glide ring) which allows it to slide evenly through the fire piston housing. This is a required component. The glide ring is split on the outside to facilitate its removal and installation.
· The fire piston is mechanically connected to the fill poppet at the rear of the marker by the fill poppet rod, which extends through the middle of the dump chamber. When the fire piston moves forward to fire the ball, the fill poppet rod also moves forward, and seals the dump chamber from the air supply while firing.
· The only notable difference in the fire piston and housings over the years is that the 1998-2000 housings used a flathead screwdriver for removal, whereas the 2001-2002 housings used a 3/16" allen wrench. The colors of parts in the picture may be different than your marker.
· There was once one "aftermarket" fire piston available, called the Rokit piston from Planet Eclipse. The Rokit piston didn't operate any differently, but it was allegedly made into a stronger design that wouldn't break "as much". As the story goes, if your fire piston ever broke, you were suggested to purchase the Eclipse replacement to prevent any further problems in the future. Most people didn't bother with the Rokit piston unless they had a problem with the stock one since it didn't change performance, just theoretical reliability.
Fill Poppet:
The fill poppet is a valve-acting assembly in the rear of the body. Its purpose is to control the inlet of air pressure into the dump chamber. The poppet's position (open or closed) is determined by the position of the fire piston at the front of the marker. The fill poppet rod connects the two, so when the fire piston moves, the fill poppet moves. The disassembled poppet is shown below, partially assembled on top and fully disassembled on bottom.
While idle, the poppet is held in the "open" position, allowing air to enter the dump chamber. When the fire piston moves forward to fire the marker, the fill poppet is pushed closed by a spring behind it, which seals off air entering the dump chamber.
· The fill poppet is both a required part for the marker as well as a performance-boosting device. If the fill poppet weren't present, the fire piston wouldn't have enough return force to shut after firing (meaning air would continuously leak out the barrel). Alternately, the sealing of the dump chamber also serves to boost the efficiency of the design. This is done by the tank always being shut off from the open atmosphere while the marker is in use, which helps to prevent excess pressure from being lost.
· The fill poppet is removed using a 7/8" wrench or socket onto the housing at the rear. This will remove the entire assembly, which can then be further disassembled by using a screwdriver through the back. The later 2001-2002 models replaced the screwdriver with a 3/16" allen wrench.
· There was once one "aftermarket" fill poppet assembly available. It was made by PMI/Evil, called the Evil Shocker Worm. However, due to Evil's inept marketing campaign, most people thought this was simply called "The Part" or "The Part for the Shocker". What the Shocker Worm does is replace the stock on-off poppet valve with a continuous airflow. The airflow is restricted, however, to still allow the fire piston to close like normal. The amount of "flow" through the Worm is adjustable using a 1/8" allen wrench through the rear, which is a required adjustment depending on your input pressure and board's fire pulse setting.
The advantage to the Shocker Worm was increased efficiency when properly timed with the marker. However, the disadvantage is that many people were never able to get their Worm to function correctly in the first place. It has a few design quirks and tends to require periodic re-timing after a few cases of use, at best scenario.
Personally, I've not had much success with the Worms. Those that I've used didn't work for very long before either breaking or requiring more adjustments, then eventually breaking in the end anyway. I've always ended up removing the Worm after experiencing issues with it. Whether or not you want to deal with the Worm is up to you.
Bolt Piston:
The final internal assembly of the Shocker is the bolt piston. The purpose of the bolt is to facilitate the reloading of the marker's chamber. When idle, the bolt is held in the forward "closed" position, with the ball in front of it (ready to fire). The marker fires the current ball, then after a few milliseconds the bolt will open to load a new one. The next ball in the ballstack falls into place within the breech, then a few milliseconds later the bolt closes again and loads this ball for firing.
The bolt piston is controlled by the 4000 "bolt" solenoid. The bolt solenoid is a four-way valve type, which means it has two possible positions. The bolt solenoid holds the bolt closed while the marker is idle, then when it fires the solenoid switches positions to actuate the bolt open. After the next ball loads, the solenoid switches back and pushes the bolt closed again.
· The time the bolt stays in the open position is controlled by the marker's circuit board (specifically, the bolt pulse setting). The bolt pulse is designed to allow the bolt enough time to load the next ball, then automatically close afterwards. If the next ball fails to load in time then the bolt will close anyway, and the next shot will be a dryfire (no ball will be fired). If you experience this problem then you should increase the bolt open time on your board.
· This type of issue is normally countered by the addition of anti-chop eyes to monitor the state of the chamber (loaded or unloaded). However, the Shocker was designed before the major introduction of eyes in paintball markers, and as a result the marker was never made to accept a drop-in set of eyes like most current markers out there. It's true that eyes can be custom-installed on the marker using a new board and new electronics, but this type of work is expensive unless you can do it yourself.
· The bolt piston is removed from the rear of the marker by simply gripping the knurled knob and unscrewing it. Once the threads disengage the piston can be slideably removed. It's a long component so be sure to exercise care to avoid bending it in any one direction (pull it as straight out as possible). You'll notice the bolt tip at the front end can be moved back and forth, attached to a metal piston rod (also known as bolt ram). The bolt assembly can be disassembled by removing the endcap with a flathead screwdriver. This was changed to a 3/16" allen wrench on 2001-2002 models. After the endcap has been removed, the rear of the bolt piston is visible within the main housing. Using a fathead screwdriver (or 1/8" allen wrench if 2001-2002), the bolt piston can be unscrewed from the bolt tip. However, since the use of loctite or other threadlocker is suggested to hold the ram with the tip, a lot of torque may be needed to separate the two.
· The bolt has two bumpers which are used to soften the movement of the bolt back and forth. The "close" bumper is located right in front of the large diameter on the piston rod, inside the main housing (it's not visible unless you completely disassemble the assembly). The close bumper softens the impact of the bolt when it moves forward. The other bumper is called the "open" bumper and is located between the bolt tip and the front of the main housing. It's used to soften the impact when the bolt tip opens and collides with the front of the piston housing.
· Shocker Sports used aluminum bolt tips until 2001, at which time SP introduced an aftermarket delrin bolt tip called the Voodoo Shocker bolt (there was also a delrin Voodoo Impulse bolt, they aren't compatible). The Voodoo bolt was made a stock part with 2002 models. New Designz also produced a variant of their own delrin bolt tip, called the Pro-Equalizer Shocker bolt (different than the Pro-Equalizer Impulse version) but they were discontinued after 2002. One of the two stock aluminum bolts is pictured in the pictures above.
· The addition of the delrin bolt tip allowed the bolt to move slightly faster, so the cycling time was increased by a small amount. The difference wasn't major though so the markers were still capped at the same speed (13-bps max). Regardless of this, there was often an increased efficiency amount noticeable after switching from aluminum to delrin. Again not a large difference, but something nevertheless. The other advantage of the delrin tip is reduced breech wear during regular use.
Fire Piston Seal Ring:
There's one remaining component that interacts with the internals, yet doesn't really fit into the above sections. It's a yellowish brass ring that seals against the fire piston, located on the inside of the body. The purpose of this ring is to seal off the dump chamber, as mentioned in the above section about the fire piston.
The brass ring doesn't require any maintenance of its own, and really shouldn't be removed unless absolutely necessary (reanodizing, total rebuild, etc).