There is no such feature yet.
- trigger a timer - I can probably add that
- hold until it's fired - it's impossible to know in a script when the gun actually fired. The only way I can think of is adding a pre-configured delay

is there more documentation for this trying to set it up so it triggers a timer and not a weapon and that it will hold that barrel until its fired

Most guns should work fine. There are may be issues with railguns and autocannons timing due to how they are implemented in the game. The welder or timer are the only intended way of telling the script where they should fire.

can you controll the angle at which the guns fire relative to the rotor besides the placement of the welder? my guns dont seem to line up properly in the barrel

Yes

does the script allow the guns to be placed on multible subgrids on one rotor?