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FBM Delrin Triggers
By Bill Mills - Nov 2004

In the 1980s and into the 90s, Delrin* caught on as a material for aftermarket paintgun bolts and pumps.  Delrin is an acetal resin developed by DuPont in the early 1950s.  It is a polymer derived from formaldehyde that was originally called “synthetic stone” by Dupont’s research staff, and was later given the brand name of Delrin.  While Delrin is a strong material, it has other qualities that are very unlike stone.  From a manufacturing aspect it is easily machined with the same tools and equipment used to create parts out of aluminum and steel.  From the applications point of view, Delrin is not only strong, but it is also considered a self lubricating material.  It can be used as a bushing material between metal parts to reduce friction and wear, and it can also be used to make whole parts that will exhibit little friction or wear as they interface with metal parts.

Fireball Mountain has found another application for Delrin – triggers.  They manufacture two styles of trigger for the Matrix, Angel LCD, IR3, Speed, Matrix and DM4 using Delrin as the main material. 

The selection of Delrin means that the trigger is lightweight, unlikely to bind against its hinge point or sides of the grip frame.  One of the advantages FBM cites for their Delrin triggers is that with less mass, they are less likely to have problems with physical trigger bounce, and in most paintguns can be used without a trigger return spring.

The first design, Fireball calls Original.  It is a simple, single wide radius curve.  The second design, called the Wave is a reverse of many two-finger trigger designs, and is laid out in an s-curve shape.

For review the Wave trigger was tested on an LCD Matrix.  Installation was straightforward but required custom fitting.  The process began with the removal of the Matrix’ wraparound rubber grips, followed by disconnection of the power and solenoid wire leads from circuit board.  Once unplugged, the grip was removed from the receiver, and a pin punch was used to gently tap out the trigger pin.  The stock trigger was then easily lifted out.

It was discovered at this point that the FBM trigger would not simply drop into place.  It was wide enough that it would bind against the grip frame, too tightly to reset after each shot.  A few minutes with a fine flat file was enough to adjust the trigger to a perfect fit with the frame.  In retrospect, the oversize fit can be advantageous, as filing the trigger ensured a perfect fit to the frame without any side to side slop that would be present if the trigger had been undersized.

The trigger pin was easily tapped back into place with a pin punch.  Adjustments were made to the trigger’s set-screws.  The next steps were to reattach the wires to the circuit board, and reconnect the grip frame to the receiver with its two screws.

Both of the FBM trigger designs for the Matrix feature twin set screws, just like the stock triggers.  The front-most screw adjusts the forward trigger travel limit, while the rear screw adjusts its rear travel limit.  The forward travel limit screw must be adjusted while the grip frame is not attached to the receiver.  Turning it in or out directly affects the trigger position and can be checked with test pulls to make sure that the trigger switch is reliably released after each pull.  The rear limit screw, like the screws on stock LCD Matrix triggers was installed with its hex head on the top side.  This presents a slight problem when adjusting.  It requires that the grip frame be removed to make an adjustment, but since the screw works by contacting the receiver, the only way to check the adjustment is to place the grip frame back on the receiver.  For review, the rear adjustment screws were removed, then reinstalled in the triggers with the hex heads on the bottom.  This allowed for the rear trigger limit to be adjusted with a ball end hex wrench while the grip frame was mounted on the receiver.

Testing the trigger, FBM’s claim of reduction in physical trigger bounce proved to be true.  A limiting factor on how short a stock Matrix LCD can be adjusted lies in the trigger bounce.  A very short trigger pull can be achieved by adjusting the set screws, but firing a few shots with air can often show that the adjustment was made too tight, and the ‘gun will fire occasional double shots as the recoil of the receiver shakes relative to the trigger.  While a double shot here or there might not be a concern to some players, it is a legitimate safety issue, and more often than not will be caught by a tournament referee examining the ‘gun - resulting in disqualification.  With FBM’s Delrin trigger it was possible to adjust to shorter trigger pulls without having physical trigger bounce become a problem. 

In practical use, the trigger performed well, operating smoothly, and was easy to fire quickly.  The two shapes provide quite different feels, and which of those is better for any given player, would largely be an issue of personal taste.
 

*Editor’s note: Delrin is a registered trademark of the DuPont corporation and their attorneys get snippy if we don’t remind our readers of that fact.
 

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