A plunger arrow rest, often simply called a "plunger" or "pressure button," is a crucial component in archery, particularly for recurve bows, designed to fine-tune arrow flight and compensate for a phenomenon known as archer's paradox. It works by providing a spring-loaded, adjustable resistance that the arrow pushes against during the initial phase of release, ensuring a clean and consistent launch.
What is a Plunger Arrow Rest?
A plunger arrow rest is typically a small, cylindrical device mounted through the riser (the handle section) of a bow. It features a spring-loaded button that extends outwards, holding the arrow away from the riser's side. This button retracts slightly as the arrow is released, allowing the arrow to flex around the bow's riser without making contact, thereby correcting its initial trajectory.
Key Components
Understanding the parts of a plunger helps clarify its function:
- Body/Housing: The main cylindrical part that threads into the bow's riser.
- Spring: Located inside the housing, it provides the outward pressure for the button. Different springs (soft, medium, hard) can be used.
- Button/Plunger Pin: The small, rounded tip that makes contact with the arrow shaft, pushed outwards by the spring.
- Adjustable Cap/Spring Tensioner: Allows the archer to increase or decrease the spring tension, dictating how much resistance the arrow encounters.
- Locking Ring: Secures the plunger in place once adjusted.
The Mechanism: How a Plunger Rest Works
The plunger rest's operation is a dynamic process that begins the moment an arrow is released:
- Arrow Placement: The arrow is nocked onto the string and rests against the plunger's button, which holds it slightly away from the bow's riser and aligned with the string.
- Initial Release & Flex: When the archer releases the string, the string pushes the arrow forward. Due to archer's paradox, the arrow doesn't travel in a perfectly straight line initially. Instead, it begins to flex outwards, away from the bow's riser.
- Plunger Yields: As the arrow flexes outwards, it presses against the plunger's spring-loaded button. The button retracts slightly, allowing the arrow to bypass the riser without impacting it. This controlled yield is essential for avoiding erratic flight caused by the arrow hitting the bow.
- Arrow Rebound and Clearance: After the initial outward flex, the arrow begins to rebound or flex back inwards due to its inherent stiffness (known as its spine). If the arrow's spine (stiffness) is correctly matched to the bow's draw weight and the plunger's tension, the arrow's tail will flex back inwards in a smooth, harmonic way. This harmonic flexing allows the arrow to completely clear the plunger button and the main arrow rest body without any further contact as it leaves the bow. This ensures a clean exit and stable flight.
The Critical Role of Arrow Spine
The interaction between the plunger and the arrow's spine is paramount. An arrow's spine determines how much it flexes.
- Too Stiff: If the arrow is too stiff for the bow, it won't flex enough, causing it to push too hard against the plunger and "kick" off to the side, leading to an inconsistent shot.
- Too Weak: If the arrow is too weak, it will over-flex, possibly bending around the riser too much, which can also lead to poor flight or even contact with the rest as it tries to rebound.
- Correct Spine: With the correct arrow spine, the arrow will flex and rebound optimally. The plunger provides the initial clearance, and the arrow's natural harmonic flexion ensures it clears the rest system entirely for accurate flight.
Why Use a Plunger Rest?
Plunger arrow rests offer several significant advantages for archers:
- Corrects Archer's Paradox: It's the primary tool to manage the arrow's paradoxical flight, ensuring a straight trajectory.
- Fine-Tunes Arrow Flight: By adjusting the spring tension and the plunger's position, archers can precisely tune their arrows for optimal flight and consistent groupings.
- Compensates for Release Imperfections: A slight variation in an archer's release can be somewhat mitigated by the plunger's flexibility.
- Versatility: Compatible with various arrow materials (carbon, aluminum, wood) and arrow rests (like flipper rests or magnetic rests).
Adjusting a Plunger Rest
Tuning a plunger rest involves adjusting both its spring tension and its in/out position (how far it extends from the riser).
- Spring Tension: Controls how easily the button retracts.
- Higher Tension (Stiffer): Good for stiffer arrows or heavier draw weights.
- Lower Tension (Softer): Better for weaker arrows or lighter draw weights.
- In/Out Position: Determines the center shot, i.e., how far the arrow is held from the riser. This is typically set so the arrow's point is aligned with the center of the string.
Archers often use a process called "bare shaft tuning" to achieve the perfect plunger setup, ensuring their fletched and unfletched arrows hit the same spot.
In essence, the plunger arrow rest acts as a dynamic guide, working in harmony with the arrow's natural flexing characteristics to ensure a smooth, unhindered departure from the bow, leading to enhanced accuracy and consistency.
