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Shocker 03 HE Bolt Kit
By Bill Mills - August 2004
Chronograph Data

The Shocker 03 redefined the name Shocker for Smart Parts, replacing its large and heavy predecessor with a small, compact lightweight paintgun capable of high rates of fire.  What stayed in the new Shocker was a reputation for gas inefficiency, limiting the amount of paint that could be shot on a single tank fill.

Smart Parts addressed this with the High Efficiency (HE) bolt kit.

In the Shocker 03, the Bolt is the integral moving part for the paintgun’s valve, and understanding why it has limited efficiency is key to understanding how the HE bolt can improve upon it.

In the center of the Shocker’s bolt is a raised ridge with a seal, called a sail in other spool valve designs.  This sail allows the bolt to behave as a pneumatic ram.  When air pressure is applied behind the sail, the bolt moves forward, and when it is applied in front of the sail the bolt retracts.

Surrounding the front of the bolt is a firing chamber.  The firing chamber holds the bolt in place and acts as an accumulator for the gas that is going to be used to propel the paintball.  When the Shocker is at rest between shots, air fills the firing chamber.  The air comes up through the receiver, passes through a single hole in the firing chamber, and fills the firing chamber.  The firing chamber is sealed to the bolt in the front and the back.

The bolt itself has a ring of holes, which allow air to flow from the firing chamber into the bolt.  Because the bolt has a bolt guide in its center, which seals to the bolt with o-rings, the air can not rush through the bolt and out the barrel.

When the Shocker is fired, the solenoid valve in the grip frame actuates directing air which moves the bolt forward.  This chambers a paintball in the barrel and the tip of the bolt seals the breech by sliding into the receiver’s seal-forward o-ring.  When the bolt is at the front of its stroke, the ring of holes in its side are positioned forward of the front o-ring on the bolt guide.  This allows air to flow freely from the firing chamber into the bolt, and forward through the bolt face to the barrel where it propels the paintball.

At the same time that the firing chamber is venting into the breech, it is still being refilled from the gas source.  The valve works much like a water hose in valve in that it opens for a set period of time, and gas flows through it until it closes.

The Smart Parts Shocker 03 HE bolt kit works a little differently.  The kit includes a new bolt, new bolt guide and new firing chamber.  It utilizes the same bolt sleeve as the dynamics of how gas flows to move the bolt closed and open is the same as with the stock bolt.

The HE bolt guide is different from the stock primarily in that it is narrowed in diameter between its front two o-rings.  This creates airspace between the bolt and the bolt guide forming what is in essence a second firing chamber, much similar in concept to the way “low pressure” chambers are added to many poppet valve paintguns, but doing the job internally.

The HE bolt’s firing chamber looks externally much like the stock chamber, but there are a few differences. 

It is a two-piece design, rather than being machined out of a single piece of aluminum.  A front end piece locks into the main body of the chamber, secured by the snug fit of an internal o-ring.  The design allows for a lip on the inside of the front chamber face.  Another difference is that instead of a single hole, there are four smaller holes to refill the chamber.  The fit of the chamber’s two pieces necessitated a smaller opening, and multiple openings allow for less restricted gas flow.

The gas flow holes in the HE bolt are elongated and larger in diameter.  While not only does this increase flow rate, but it also serves a another important purpose.  When the bolt is forward the elongated holes open access between the breech and both the firing chamber and the air space in the bolt guide. 

The big gas conserving feature on the HE bolt is a single o-ring.  When the bolt is forward this o-ring fits up against the lip in the front of the firing chamber and blocks the chamber off from the air source.  Instead of streaming gas out at the paintball, the firing chamber is sealed off, and the air in the chamber is allowed to expand, propelling the paintball.  It is this difference that accounts for the increased shot counts capable with the HE bolt kit.  Cutting off the source gas required adding volume to the firing chamber, and fortunately there was enough space in the bolt guide for this to be possible.

Installing the HE bolt proved to be as simple as installing the stock bolt.  The process begins with removing the bolt guide and using a plastic squeegee to push out the firing chamber along with the bolt and bolt sleeve.  A light coat of Shocker Lube was applied to the o-rings of the new bolt assembly.  The same bolt sleeve was slid onto the HE bolt, and the whole assembly slid into the Shocker 03 receiver and screwed into place with a hex wrench.

The HE bolt is designed to operate with a higher dwell time than the stock bolt.  In the 03 Shocker used for review, the dwell time had initially been set to 10.5ms (30 chirps) with the stock aluminum bolt.  With the HE bolt installed the dwell was increased taking a few shots at each setting until the velocity was more stable from shot to shot, and testing was done with a dwell time of 11.5 ms (34 chirps.)  The dwell time increase is needed with the HE bolt because the fire chamber must be allowed to dump its contents with each shot, rather than simply turn the flow of gas on and off from the source.  It was noted that the velocity increased significantly between the two bolts from the 280s to the 320s, and the air pressure was lowered to bring the velocity into the proper range.  The increase in velocity was a good indicator of improved efficiency, as increases in dwell time past 10.5 ms hadn’t caused such velocity increases with the stock bolt.

All field testing – both in game and on test stand was performed with DraXxus Hellfire paint, and utilizing a matched diameter Smart Parts Freak barrel system (.687” insert.)  In use on the field, the new bolt sounded quieter, and more shots were apparent between tank fills, at over 800 shots off a 3,000 psi fill on a 68ci Max Flow system.

The stock and HE bolts were compared for velocity consistency to see if the bolt changes affecting valve recharge would have an effect shot to shot consistency both at a 1 shot per second rate and 14 shot per second rate.  Strings of 30 shots were recorded and analyzed at each rate with each bolt.  The shot velocities were averaged and standard deviation values computed.  The standard deviation is a way of quantifying how consistent a series of numbers are.  A higher value means the group of numbers varies more than with a lower value.

Something immediately apparent when comparing the two strings was that with both bolts, first shot drop off (a low velocity first shot) was apparent.  This had not been noted during an initial review of the Shocker, and variances between consistency and FSDO may possibly be due to performance differences between the stock Delrin bolt used in the initial review, and the stock aluminum bolt compared in this review.

At a rate of one shot per second, the stock bolt delivered a standard deviation of 13.8, at an average velocity of 290 fps, while the High Efficiency bolt delivered a standard deviation of 7.2 at an average 278.2 fps.  On first glance, these numbers appeared a bit extreme, especially compared to the standard deviation of 3.4 that the stock bolt had achieved with the matched Freak barrel during initial review of the Shocker 03.  

The stumbling block in the numbers was the first shot drop-off.  Discarding the velocity of the first dropped shot and calculating with the velocity of 29 shots, the stock aluminum bolt provided a standard deviation of 3.8, very close to that of the older style stock Delrin bolt.  The High Efficiency bolt was slightly less consistent at a standard deviation of 4.7.

Looking further at the data and disregarding 5% of the shots which were furthest away from the average to account for paint variances as well as FSDO (the 95% +/1 value) the stock aluminum bolt yeilded a shot consistency of plus or minus 5 while the HE bolt yeilded a value of plus or minus 3, an increase in consistency with the HE bolt.

At an increased firing speed of fourteen shots per second, the standard deviation increased with both bolts.  Discounting the first low shot, the standard aluminum bolt delivered a standard deviation of 4.1, while the high efficiency bolt weighed in at 6.8.  

Looking at the 95% ± analysis, the stock bolt gave a figure of 1 at 14 bps which was better than when the Shocker was fired slowly.  The HE bolt was not so stable when fired fast, and its 95% ± value increased to 8.

For full chronograph data click here.

In addition to measuring velocities, peak sound output measurements were taken at a distance of two feet from the muzzle, to the right of the barrel.  Five measurements were taken with each bolt and then averaged.  The stock aluminum bolt yielded an average peak sound output of 71.8 dB.  The HE bolt on the other hand yielded an average peak sound output of 63.6 dB.  The HE bolt provided a significant noise reduction over stock.

Overall the HE bolt is an easy to install upgrade for the Shocker 03 that produced noticeably improved gas efficiency, with a small decrease in consistency at high rates of fire, but better consistency at lower rates, and significant noise reduction.

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