What Is Rapidfire?
by Zak Vetter
Short Answer
Rapidfire is the ability of the RT valve to shoot VERY fast with little effort in that you do not have to pull the trigger each shot. It can reach speeds over 30 shots per second.

Long Answer
Rapidfire (often mislabled “runaway”) is a method of firing an RT valved Automag or E-Mag (see valve comparisons for info on valves). Rapidfire can reach speeds well over 20 bps and can be held at those high rates of fire for long periods of time. Rapidfire is possible because of the design of the RT valve and the “bounce” or “kick” that occurs from the valve recharging after each cycle.

When you pull the trigger on an RT valve equipped Automag, several steps occur in very quick succession.

  1. The on/off pin is pushed up by the sear allowing the air in the chamber to rush out and push the bolt forward (firing a ball)
  2. With the air chamber empty, the air from the regulator rushes in to fill the depressurized on/off chamber.
  3. This surge of air coming in is what pushes the on/off pin --> the sear --> and the trigger back to their original position. However this is where the “bounce" of the RT valve comes in. The air rushing in to refill the on/off chamber passes through the valving so quickly that the friction of it moving inside the valve heats the air up. When air heats up it expands, increasing the pressure. Increased pressure means that the pin --> sear --> trigger are pushed back with a greater force than it took to initially push. This pressure spike lasts only a moment as the surrounding metal of the valve quickly cools the air but it is that spike in pressure that you feel on your finger as the valve kicking back on you.
  4. The bolt is pushed back by the spring and the marker is ready to fire again.

Though the strength and feel of the bounce depends greatly on the regulators and operating pressures of your setup, the basic idea behind the trigger bounce is this: when you pull the trigger, after the marker fires, the trigger is pushed back to you with a greater force than you pushed it with. Below is a graph of the pressure of the RT valve when it is fired 1 time. The data and graph were made by AGD and clearly show the pressure spike after the cycle of the valve.

Now here is how rapidfire functions within this system. Let’s say that the trigger takes about 9oz to pull when the air in the chamber has had time to stabilize. When the chamber refills (as can be see from AGD’s data) the pressure spike is a visible blip that largely drops within about 10 milliseconds. This spike allows you to keep a constant pressure on the trigger that is just enough to push the trigger back again (say about 9.5oz). When you do this, the valve will fire and reset itself because the pressure spike exceeds the original stabilized air pressure in the chamber.
The gas quickly cools at which point your finger pressure exceeds the now cooled air pressure in the on/off chamber and the operation repeats itself. We call this seemingly fully automatic mode of fire “rapidfire.” (watch the video on the right). Below you can see a what rapidfire looks like in 2 shots. Notice the quick spike before each cycle.
As I describe in the what is needed page, rapidfire can reach very high rates of fire and is completely controllable in the speed at which the valve cycles. The heavier pressure the longer it takes for the recharging air pressure to exceed the pull of your finger and the more your finger pressure retards the recharge of the valve. The lighter the pressure on the trigger, the quicker the recharge of the valve and the thus, the faster the valve will cycle.

A lighter finger pressure = faster rapidfire

A harder finger pressure = slower rapidfire

Upper limits of the rapidfire I estimate to be 40+bps. My latest speed test with AIC's QLoader broke 34bps on an RT Pro.


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