Shocker SFT Spring Bolt Mod > Tech index > Shocker SFT > Adjusting and maintaining > Spring bolt mod > Tech index > Shocker NXT > Adjusting and maintaining > Spring bolt mod

Spring mod overview:
A popular modification for Shockers involves outfitting its bolt with a forward-pushing spring which assists the bolt's forward-motion when firing. Variations of this concept have been implemented as factory parts in markers such as newer Luxes. The final incarnation of Shocker spring mod has been developed and enhanced by the PBnation Shocker community and is now somewhat prevalent in the current age of Shockers.
Spring-modded HE bolt (picture from J. Fissinger)

    Fully-tuned Shockers with spring mods have the following advantages:
  • FSDO is eliminated
  • Reduced dwell time
  • Sometimes reduced input pressure
  • Air efficiency is usually increased
  • Better performance in cold weather

The downside to a spring-modded Shocker is reduced maximum firing speed (usually around 15-17 BPS), increased detent wear, and advanced tuning is typically required. The internal parts usually require homebrew modifications which often aren't available out-of-the-box, at least for older bolts. Some late-model aftermarket bolts come pre-modded, but this is not a solution for older bolts.

Springs and compatibility:
The most popular Shocker spring is called the "Rhino Spring" (sold by Rhino1XL @ pbnation) which has become the default item used in Shocker spring bolt mods. However, only certain bolts will accept a Rhino spring without modification: NDZ v3m bolt, Eigenbolt, Pooty bolt. All other bolts require modification to precisely widen the rear end of the bolt to allow spring clearance.
The one exception is a TechT bolt which comes modded for a TechT spring, which is smaller than a Rhino spring, therefore TechT bolts will not function with a Rhino spring. However, TechT bolts can also be bored out just like any non-spring bolt.

Players have experimented with cutting a shorter spring that still produces some FSDO and efficiency benefits, but has the advantage of easier tuning. Use of a "medium-strength" spring is sometimes preferred for beginning modders. Various types of light-strength and medium-strength springs are available from Rhino, Pooty, and others.

Bolt modification activity:
The bolt modification is very difficult to perform with common hand tools. Using a lathe or mill to precisely bore the bolt is strongly suggested. The diameter and depth is critical because the modified bolt will become weakened and runs the risk of being damaged if done improperly.

The modification can be done in two ways:
1. The easiest method is to drill the bolt using a large 5/8" drill bit, then carve a lead-in around the entrance to the bore. The lead-in is suggested to prevent spring binding. This modification is easiest to perform using a manual lathe. Using a handheld drill driver is too risky because the large drill bit will be difficult to control.
2. The more difficult but more-reliable modification involves precisely boring the bolt's inner surface to a diameter of 0.616" which has been found to be optimal for a Rhino spring. Again, spring binding is controlled by a small lead-in around the entrance to the bore. Boring the bolt in this way creates a flat surface upon which the spring can rest. The boring operation can be done with a precisely-aligned mill with boring head, but is generally easier to perform on a lathe.

CNC machines are not required for the bolt modification. In fact, a manual/traditional lathe is recommended over CNC because only a hand-operated machine tool will provide manual feedback, which can be useful when cutting fragile workpieces such as a Shocker bolt.

The first step in tuning the marker is to set a dwell time that allows the bolt to fully cycle for each shot. Choose an input pressure of your liking (generally 170-psi or above) then adjust dwell time until the marker begins the full cycle with no paint loaded.
Once the marker fully-cycles, increase dwell a further 1-2 milliseconds (4-8 chirps on SP Shocker/Nerve board).
Load paintballs and attempt to chronograph the marker by adjusting the input pressure. If you are unable to achieve desired velocity, you may need to increase dwell setting then re-chronograph the marker.

Most players are able to use a low dwell setting such as 8-9 milliseconds (19-24 chirps on SP Shocker/Nerve board). Every marker is different and the o-ring fit will also affect velocity performance. Some players prefer to use tight o-rings to prevent any chance of leaking during firing, while other players lean toward loose-fitting o-rings that create minimal friction but sometimes require more lubrication. There is no single perfect method for marker tuning so experimentation is required!