Excaliburs were first released around 1998, so they're relatively old in the timeline of electronic markers. The Excal internals layout and interaction is similar to that of an Autococker in that there are separate sections of the marker body dedicated to firing the ball (using a hammer and valve) and another designed to operate the bolt, independently from the firing action. The creator of the marker (AKA) commented on his original designs being a more literal electronic version of the current Autocockers at the time, however after further development he ended up rebuilding the marker from the ground up, and the product of that became the Excal.
Excals use an entirely-integrated body design, whereby all internals (hammer piston, bolt piston, pneumatics LPR, etc) are housed within the body and not on the outside. Additionally, the components are based on piston designs and use mostly base-mounted seals, meaning there aren't any hose or barb connections. This design aspect is very reliable and I see it as one of the gun's best advantages. These features combined allow Excals to be much more integrated than a typical Autococker, being that there is virtually no mechanical timing adjustment.
Operation:
As mentioned, in one sense Excals were designed to be upgraded Autocockers, and are actually quite similar in operation. The hammer/valve cartridge fires the ball, afterwards the bolt recocks to load the next shot. Excals are closed bolt markers so their ROF is slightly limited compared to the super-markers of this day and age, but still able to crank out 14-bps or more. Excals operate similar to the main electro-marker of the time, the original Shockers from pneuVentures, and later Smart Parts, which also use an independent firing cycle and operate as closed bolt.
Excalibur fast |
Excalibur slow |
The animation isn't perfectly accurate, most notably when it comes to how quickly some parts move in comparison to others. In reality the limiting factor for an Excal's maximum ROF is how quickly the bolt can move. THis ends up being over 15 milliseconds in each direction, with more time being used when the bolt opens up (since there's a much larger volume of air being vented when it opens compared to when it closes). This tends to place a physical cap of around 14-15 bps on most Excals out there, unless they're able to vent air and move the bolt abnormally quick.
Pneumatics Airflow:
There aren't many practical reasons to explore the internal passageways of the marker body, but I want to mention it anyway since it's quite a complex system. This consists mainly of a central LPR pressure chamber drilled in from the rear of the marker body, which is filled with output pressure from the LPR at the front of the body. Here's a diagram I made a while back...
The diagram shows the central LPR pressure chamber between the left and right body bores. It's fed by the LPR at the front of the marker and outputs air to the two solenoids (red). Each solenoid has its own set of outputs (green): an idle output and a firing output. In both cases, the firing output is the front port, and the idle output is the rear port. This leads the bolt piston to remain in the forward position, and the hammer piston to remain in the rearward position.
The body is designed such that the solenoids' mounting screws pass directly through into the internals' bores, leading to unpressurized areas. This makes the bodies easier to produce, however can lead to difficult diagnosis when one of the cartridge external o-rings springs a leak.