The complete gun swap looks like a very high possibility.
I pinged the connections and noted functionality on paper.
They have pcb markings.
The wire colors don't match, but there is a correlation in both name and function.
Here's what I have found on the old gun
It has 4 circuit boards
Sensor:
Vcc, red
OTP, orange (the sensor)
Gnd, black and brown
Switch
Reset, blue
Vcc, red
Set, green
Gnd, black
Vcc trough resistors to other signals
It is 2 positions
Depending on the position, either set or reset goes to gnd
Button
Reload, white
Gnd, black + brown.
When pressed reload goes to gnd
Trigger
Vcc, red
R1, purple
S1, yellow
Gnd, black
Vcc trough resistors to other signals
When open, R1 to ground
When closed, S1 to ground.
On the new gun,
Same difference.
There's 3 position to the switch (c, 1, 2) and added 2nd player labeled wire.
Seems like the old gun was hardcoded to player 1 while the new gun had a selection.
Here's the pins
Vcc, black
Reload, brown
Reset, red
Set, orange
R1, yellow
S1, green
Opt-trig, blue
2nd player, purple
Gnd, gray (and black, which goes to the shield of the cable)
There's matching resistors...
Here's what I believe is the correlation between the guns (edited to reflect new data)
Old - - - new
Red-black
Orange-blue
Black-gray
Blue-red
Green-orange
Brown-gray (2nd ground)
Purple-yellow
Yellow-green
White-brown
N.C. - purple
Seeing how I will not be able to use the old gun as is until there is at least a disconnect connection to pass trough the front wall of the arcade, I'll go ahead and splice them up to see where we end up.
If this works, I'll finalize the setup.