How to Make a Crossbow Trigger (Simple Mechanism)

A trigger is a system that initiates the shooting sequence of a weapon, be it an air gun, a crossbow, or a speargun. Other non-shooting mechanisms such as a trap, a switch, or a quick-release can also be started by a trigger. A trigger ensures the small amount of applied energy is transferred to release more energy.

The difference between the triggers of firearms and quality crossbows is quite simple to understand. Firearms just need the trigger to activate the hammer to hit the primer, which ignites the gunpowder to launch the projectile. However, crossbow triggers are not intended to strike the primer but are intended to release the load allowing it to transfer its power to the arrow.

In order to better understand what makes crossbow triggers different from other firearms, we need to take a closer look at the trigger mechanism of the crossbow.

There are two approaches to making a crossbow trigger:

1.   Metal-Based trigger
2.   Wood-Based trigger

Metal-Based Trigger:

The tools needed for making a crossbow trigger are:

• Screwdriver
• Dremel Rotary Tool
• Cutting Wheel
• Jig Saw or Small Metal Saw
• Pair of Pliers

The required materials are:

• Aluminum Plate            5mm
• Tension-spring              20mm
• Spring Wire-thickness 0.5 to 0.8mm
• 4 Screws                          5-8mm
• 5 Screws                          12mm              
• Plastic Spacers               6mm
• M3 nuts

You can also use wood instead of aluminum; it depends on the strength of your crossbow.

Method:

Print the design of baseplates and other two parts on a white paper, and cut it out using a scissor. You can design it yourself, or use existing and proven designs from various contributors over the internet.

Now transfer these outlines on metal. An acrylic-based marker would work best for marking out an aluminum surface.  

Next, take the aluminum plate (it should not be too thin to bend easily), drill two holes of equal size, one for holding the tension spring and other for mounting, and two other holes for the stopper screws.

Place all the other screws on the cover plate and ensure everything is in its place including the lock parts. Finally, screw the M3 nuts, and perform testing of the trigger to ensure it works fine.   

Wood-Based Trigger:

Wood is an alternative to the metallic trigger approach. Compared to metal, wood is less malleable but can easily be carved into a required shape, which can be difficult with metal sheets.

Take a thin piece of pinewood and draw an L-shape on it with a pencil. The horizontal side of the “L” must be slightly smaller than the box you carved in the stock of the crossbow for the trigger system. Now cut the L-shape out of the wood using a saw. This little L-shaped piece of wood will be the trigger for your crossbow. Sand it up smoothly to avoid splinter cuts.

Next, carve a 1/8 inch channel across the small segment of the L-shaped wood by using a chisel. Once a smooth channel is created, drill a small hole (to fit the nail you are using) on the center of the wood piece, just below the corner of the L.

The last step is to attach the trigger to the wood stock.  For this place the L-shaped trigger with the groove facing upwards and the L pointing forward in the rectangle opening. Do make sure that it has space for movement without touching the back of the hole. Lastly, sand it again to fine-tune the trigger.

Use a hammer to push a nail through the stock and hold the L-shaped trigger in place at the angle.

Post Checks

After successfully creating and fixing the trigger on the crossbow, the testing phase can commence.

a. Stress Testing:

Ideally, the components of the trigger should withstand adverse factors that apply to them, for example, the jerk created by firing a bolt. The heavier the bolt the more jerk should be applied to the overall crossbow including the trigger components. A good way to perform stress testing would be to take multiple shots from variously sized bolts and with different draw weights to determine if the trigger can withstand stress of all kinds.

b. Safety Testing:

Another post-implementation check would be to test the safety features of the trigger such as its prevention of accidental misfire and ease of triggering. If the crossbow has additional safety features implemented to prevent dry fire, the user must ensure that the trigger is compatible with it.

Ease of pressing the trigger can be a convenience and a safety hazard at the same time. If the trigger can easily be pressed, you might want to consider tightening up the tension string further.     

c. Robustness:

It is recommended to weather your trigger with paint or other anti-corrosion material to prolong its durability. The use of oil-based weathering materials can affect the trigger usage by making the surface slippery and also prone to attract dirt particles.  

For wood-based triggers, anti-termite solutions can be applied over the trigger to ensure its longevity.   

Conclusion

Making your own crossbow’s trigger can be a fun experience and also an economical option in case your existing trigger has worn off and you do not want to replace it with an expensive, off the rack trigger. This activity will certainly add to the user’s skill set and, with added experience, can also enable them to develop industrial standard and high-quality triggers.