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Tech index -> Shocker NXT -> Parts of a Shocker -> Firing assembly design & theory

This page contains expanded technical information on the operation of the marker. There's a lot of information to go around so please believe me when I say it's difficult to organize well. For every page I put on the site there's another five pages of technical ramblings that I'm leaving off.

Design Definitions:
This is the simple version of how the marker operates. When the bolt moves forward, air passages within slide over an o-ring on the bolt guide which allows pressure within the fire chamber to expand out the bolt face and fire the ball. After firing is complete, the bolt is retracted backward, and these ports become closed off from the bolt face, preventing the release of additional amounts of pressure. The marker waits in this state until it fired again.

This type of design is generally referred to as a spool valve firing mechanism. This generally describes a one-piece moving assembly (bolt in this situation) which uses axial seals to release pressure to fire the ball. These designs are often viewed as significantly less complex than the more "traditional" stacked-tube designs that many previous and current markers utilize/d. Stacked tube designs involve a hammer, percussive valve, bolt, and a number of connections and housings between them. The stacked hammer design was invented in the late 80's / early 90's and is the descent of some modern markers, but spool valve markers share a differeny ancestory (used in locomotive, food production, and other industries prior to becommming poopular in paintball).
The advantages to this type of design generally include decreased recoil, higher air efficiency, decreased energy used per shot, and decreased shot volume (more quiet). Similar designs can be found in several other markers, including the Matrix and DM series markers, Ion/Epiphany, FEP Quest, and some others. In the future we may come to see additional designs like this, since it is a very simplistic method of firing a marker with many possibilities for modification.

Firing Assembly Synopsis:
Now for some technical information and further explanation of the firing cycle. You may wish to use the first animation listed below for reference. While the solenoid rests idle, the front portion of the bolt sleeve is pressurized, which holds the bolt in the rear/open position. The fire chamber is filled with pressurized air, ready to be released when the bolts fires. To fire the marker, the solenoid energizes and switches its internal valve, which is connected to the bolt sleeve. This causes the front of the bolt sleeve to vent its pressure while at the same time the rear of the sleeve becomes filled with pressure. This action drives the bolt forward. Once the bolt reaches the end of its forward stroke, the ring of porting at the front will cross over the tip of the bolt guide and all the air pressure within the fire chamber will be released to the inside of the bolt and out the front, firing the paintball in the chamber. After the dwell time expires, the solenoid switches back which vents the rear of the bolt sleeve and pressurizes the front. This retracts the bolt and also opens up the fire chamber in the HE designs.

The marker's bolt will be actuated upon the venting/pressurizing that's operated by the solenoid valve. The most important factor here is the use of the dwell time, which is the time the solenoid remains energized, which translates to how long the bolt takes to move forward and release pressure. The dwell setting must be set high enough to allow the bolt to cycle forward and dump pressure to fire the ball. This is my definition of dwell and what it is used for.

The solenoid's air passages are connected to the bolt sleeve using threaded rods called solenoid inserts. These rods are used to shunt solenoid pressure to different parts of the gun as needed. Pressure from the inserts is exchanged with the bolt components by ports drilled through the bolt chamber wall (they are vertical in the bottom of the body, covered by the set screws on the bottom).

With all that said, here is the first marker animation, of the stock bolt assembly.

Seen above is the stock bolt animation. Click here for a slower version. Please note that Shocker NXT markers come with the upgraded SP HE bolt as stock (animated below).

Bolt Moving Speed:
No matter what paintball marker you're talking about, it's always important to remember that the dwell time isn't just the time the bolt remains forward. In reality, the action of the bolt shifting to the forward position takes several milliseconds to complete, then the rest of the dwell time is taken up by the bolt waiting in the foward position while it releases air to fire the ball. Generally speaking, the majority of the dwell time on spool-based markers is taken up by the bolt moving forward. Most spool markers take little time to release air, so the majority of the dwell is just used to get the bolt closed. This is due to any number of characteristics, including the port size and length, pressure, and design of the bolt.

The Shocker in particular usually takes 1-2 milliseconds in the forward position, while the rest of the dwell time is used to move it there (8-10 ms or higher). Other types of spool valve markers tend to require longer to release their pressure since the dump chamber is located further away from the chamber. The design of the Shocker is such that the proximity between the fire chamber and the breech reduces the amount of time it takes pressure to release, as well as limiting the amount of energy that is wasted in the release itself. This makes the Shocker one of the foremost spool valve designs due to the placement of the dump chamber alone.
This is contrasted to some other spool valve markers, such as the Ion or Matrix, where the dump chamber is located at the rear of the marker. These designs require air be shunted through their bolt sleeves to reach the bolt face. As a result they tend to require 1-2 additional milliseconds to fully dump their pressure. Please note that these are not theoretical figures; I only reached these numbers after extensive real-time testing and evaluation.

This is an important factor when it comes to the type of solenoid used in the marker (of which there are two), and is discussed in the solenoid comparison section. Please refer to the Related Links.

Solenoid Dynamics:
The solenoid valve is fed through the left solenoid insert rod, on the left side of the marker body. This section of the marker is fed by the LP air supply in the vertical adapter by a single 0.046" port at the front of the body (smaller than 1/20"). This port is drilled in small size specifically to prevent the solenoid's air supply from being purged by the fire chamber when the marker fires the ball. This means that if a larger port or series of ports were used, the fire chamber would essentially steal pressure from the solenoid and cause massive cycling problems (inconsistency, velocity dropoff, in extreme cases the solenoid wouldn't be able to retract the bolt). This is a specific design of the marker and shouldn't be tampered.

Since the air supply is relatively small, the rear of the bolt sleeve component is converted into a small air pressure reservoir to help resupply the solenoid. In essence this acts as a solenoid volumizer to ensure adequate pressure is always available for firing the fastest speeds possible. The pressure reservoir is isolated from the fire chamber since it is fed through the left solenoid insert as well.

Bolt Moving Force:
The design of the bolt allows it to freely move forward with an approximate force of 15 pounds, give or take 1-2 pounds depending on the input pressure. Additionally, the stationary portions of the firing assembly act to absorb smaller amounts of force, which in practice serves to decrease the total moving force of the bolt by additional, albeit smaller, amounts. This special function of the Shocker makes it quite impossible for the application of an additional regulator (LPR) to drop the pneumatics pressure any further. This is because, when the pressure actuating the bolt is reduced, the force driving the bolt will see more reduction and prevent the marker from fully cycling. It is for this reason that the Shocker doesn't readily accept an LPR. It is true that some developers have released their own LPR kits, however as said, the practical benefit of these is low.
A frequently asked question is why, then, does the Quest marker use an LPR? This is because the Quest bolt uses larger surface area to move. Force [in this case] is derived by multiplying pressure times surface area, which is low with a Shocker. Quests use larger surface area and thus their design benefits from the use of an LPR. Additionally, the Quest bolt moves forward with nearly twice the force that it moves while traveling back. This is again due to the surface area of the bolt cross section.

Aftermarket Bolt Assembly Designs:
· SP HE bolt, aka high-efficiency bolt, aka Turbocharger bolt: The HE bolt from Smart Parts uses a special sealed fire chamber design to gain its efficiency benefits over the stock bolt. This is an upgrade for the older SFT models, or a stock feature on the current NXT. The HE bolt uses an added o-ring located on the surface of the bolt, inside the fire chamber, to seal off the input ports on the chamber when the bolt is in the forward/firing position. This serves to prevent additional amounts of pressure from entering the chamber while the bolt is firing. The stock bolt in comparison, dumps pressure out the bolt face continuously as long as it stays forward. Even with properly-set dwell timing, there will always be a benefit to sealing off the air supply from the bolt face during the shot. The added benefit of this design is that the placement of the bolt's sealing o-ring allows it to act like a spring when in the closed position. Pressure on the other side of the o-ring pushes against it and helps to blow the bolt into the open position when it recocks. This helps to conserve energy use and optimize the firing cycle.

Pictured above is the SP HE bolt. Click here for a slower animation. This is also an animation of the NDZ v3 bolt, which functions using the same operation.

· NDZ v3 bolt: This uses the same design as the SP HE. The only functional difference is that the NDZ fire chamber is designed to hold more volume, thus allowing the NDZ bolt to use a single row of ports instead of the elongated ones that the HE bolts use. The NDZ bolt functions at a lower pressure but this isn't necessarily a performance increase, rather a different way to accomplish the same task (it's a misconception that lower pressure will give you higher efficiency).
Previous versions of the NDZ kit functioned similar to the stock bolt except with added fire chamber volume. The version-3 kit uses the same HE technology patented by SP in the HE bolt. Specifically, the Stinger v1 kit was essentially a replicated stock bolt with some modified features (angled porting, added air volume for the fire chamber) and the Stinger v2 was the same as the v1 except for the high-volume fire chamber that the v3 version utilizes.

· Evolve bolt: The Evolve bolt was the first aftermarket assembly to be released for the Shocker. It has since been redesigned to a more reliable version, but the original version functioned relatively the same. This bolt also uses a design which seals off input during firing, however the Evolve version works a little differently than the HE bolt. Instead of placing the added seal on the outside of the bolt (like the HE) the Evolve bolt places the added seal inside the fire chamber itself. The bolt is then notched to allow air around the seal when in the rear position. This notching reflls the fire chamber while it's open and seals it off when forward/closed. The benefit to this is a perfect seal on the bolt, however the design is difficult to machine correctly, and has some technical problems getting all parts to evenly seal at once. This design is patented by Evolve.

Pictured is the Evolve bolt. Click here for a slower animation.
· Evovle ULP: This is the same as the SP HE / NDZ v3 bolts, with modified features such as porting and o-ring placement.

· Freeflow bolt: The design of the freeflow bolt is a modified stock assembly. It uses a large, moving ring section to attempt blocking off the air input to the fire chamber, but it doesn't seal it completely. The design isn't as reliable as the other bolts, and isn't as beneficial when totally functional. Previous versions of the Freeflow bolts used different porting patterns but the basic design never changed. The Freeflow bolt was discontinued when Freeflow Technologies went out of business, discontinuing any and all support for the parts.

Related Links:
· Stock bolt manual scan
· Solenoid inserts
· Solenoid

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Tech index -> Shocker NXT -> Parts of a Shocker -> Firing assembly design & theory