Shocker SFT NDZ Adjustable Bolt Guide > Tech index > Shocker SFT > Adjusting and maintaining > NDZ adjustable bolt guide

New Designz (NDZ) adjustable bolt guides are a unique Shocker upgrade that allows a new level of tuning for the firing cycle's mechanical dwell (a term that NDZ uses to describe the point during the bolt movement at which the air pressure is released). Typically, when using traditional Shocker bolt guides, the burst of air pressure is released when the bolt reaches the full-forward position, and the bolt's whole set of air ports are allowed to vent. Using an ND adjsutable bolt guide, the bolt can be set to release its air pressure later in the firing cycle, and doing this will also partially constrict the bolt's air ports.

Bolt guide mechanical dwell comparison

When the marker bolt reaches the forward position, it usually waits there for 1-2 milliseconds in order to release the fire chamber's entire air volume (this is the last couple milliseconds of the "dwell time"). Once that time has expred, the solenoid is de-energized and the bolt begins to return open, closing the valve.
If the bolt remains forward for ample time, the entire fire chamber will be released to fire the ball.
If the bolt's porting is constricted or the bolt doesn't allow the fire chamber enough time to vent, only a partial amount of stored air pressure will be released to fire the ball. Therefore, the function of the NDZ adjustable bolt guide is to alter the position of o-rings and limit this "forward" time by a very small amount, which translates to a larger change in velocity.

Use at lower velocity FPS: (indoor, Europe, etc)
Many indoor paintball fields require markers to be chronographed at a lower speed of 250-fps or thereabouts. This can be troubesome for some markers because they require lowering the input pressure so far that the marker can no longer fully cycle. For a Shocker, this pressure might be around 140-150 psi, which usually slows the bolt speed and prevents it from actually cycling. This often prevents the marker from being used in the indoor playfield.

The common solution for indoor use is to reduce the volume of stored air by stuffing an object(s) within the marker's dump chamber. A popular object is a dozen large o-rings, or several wraps of electrical tape, which is meant to suck up 10-20% of the marker's available air volume (depending on the number of objects in use). After this modification, the marker will instantly see a lower velocity over the chronograph with no adjustments to any other settings. Effectively, the bolt is still moving at the same pressure, but the stored energy avaialble to fire the ball has been cut by 15%. Therefore, the marker can now be chronographed and used indoor.

The new solution for Shockers is to limit the mechanical dwell setting by tuning the adjustable bolt guide. Often, when properly tuned, the air efficiency is increased while the marker is still ale to be used with an indoor chronograph speed.

The NDZ adjustable bolt guide uses a three-piece assembly that consists of these parts:
Threaded backplate that screws into the Shocker body,
Threaded shaft of specific adjustable length,
Threaded lock screw to prevent the shaft from moving during use.
Two new o-rings have been added to the bolt guide shaft (marked as 13/70 and 14/70 o-rings), both of which are used as bumpers for the new components. A third o-ring is added between the lock screw and the shaft (marked as another 14/70 o-ring). All three of these new o-rings are meant to prevent the guide from locking up when adjusting.

NDZ bolt guide

The shaft is adjusted with a 3/16" allen key (same wrench used to remove the stock bolt guide) whereas the lock screw is adjusted using a slightly larger 7/32" allen key. You will use this 7/32" allen key to remove the bolt guide for regular maintenance.
Like the stock bolt guide, this one uses a pair of 12/70 o-rings at the front and a single 22/70 o-ring at the rear. The 12/70's are used to seal the bolt, but the 22/70 just acts as a floating seal.
The NDZ bolt guide is an HE-style part, so it will function with most HE-style bolts and other parts. The NDZ guide sometimes doesn't work with an Evolve v1/v2 bolt, due to machining changes.

I recommend making adjustments to the bolt guide outside of the marker body. This will make it easier to view the shaft's length, and will also help to avoid any problems with lodging the threaded backplate into the body.

The best way to adjust the guide is to measure the length using a ruler or slide, then compare it once you altered the length by a small amount. For comparison, I measured the length of the factory bolt guide from the base of the rear bumper up to the edge of the front o-ring groove (seen in the image below). When measuring the NDZ guide, you MUST measure with the large bumper installed.
The default length for the factory bolt guide is approximately 3-5/8 inches or 92.1 millimeters.

Stock length

When adjusting the bolt guide, the bolt guide's shaft needs to be screwed inward if attempting to constrict the bolt ports. Small adjustments are best, but this requires more time for tuning (and more test firing). My definition of small adjustments is one-quarter or one-half of a turn per test. Very small changes in length will translate to larger differences in performance.

If the bolt guide's shft is screwed inward too far, the marker won't properly cycle because the bolt's porting are fully covered and the marker cannot release air pressure to fire. Some players prefer to start with the bolt guide shaft in the stock position (open bolt porting) but others prefer to start from the full-forward position (closed bolt porting).

When making adjustments, make only small differences in length at one time. This may take more than one try to get correct, but it is the best way to go about adjusting. I would suggest at most one-half turn of the allen wrench.

When you find your new shaft length, drop in the 14/70 o-ring behind the shaft then install the rear lock screw using a 7/32" allen key. Screw it in as tight as possible however be careful not to accidentally change the shaft position tightening. In some cases, you may figure out a way to screw the length of the shaft slightly short, to compensate for the lock screw pushing it forward. This is sometimes an issue, but not always (depends on the friction fit between parts).

Screw the bolt guide into the Shocker body as normal then test it out. If you are still unable to lower your velocity far enough, remove the bolt guide and screw the shaft in a bit further. If you experience problems removing the lock screw, use a large pair of pliers or channel-lock pliers to grasp the exposed depression, marked in this rendering:

Grip here

While lengthening the guide will decrease velocity, it's alternately possible to increase it by shortening the length of the guide. However, this will require a lower pressure or lower dwell to achieve the same velocity, while at the same time efficiency will most likely suffer (in this case). I don't suggest making the length shorter than the default length of 3-5/8".

Related Links:
Setting electronics and pressure