What I am making is a Ruger Blackhawk... see render. All of the parts that are supposed to move do so. Where I'm getting stuck is I want the ejector rod to push an empty cartridge from the chamber, is that possible? Also, is it  possible to have the trigger place the hammer back to the fire or default position?

Moving the hammer back:  that's easy with the newer "dependent parameters"
form of ERC in P7 and P8.   Any sort of complicated sequence can be tied to
a control dial with DP.

In earlier versions you can still do it with an animated pose file, but not
with a direct control.

The empty cartridge is tricky.  If the cartridge is rigged as a 'body part' of the gun,
you can control its ejection easily (again with DP for the complicated motion), but it
will still move with the gun after it's out, which will look weird.   (Put the gun
back in the holster, and the dead cartridge will go through the ground and then
end up standing in the air behind your knee!)

The only halfway decent solution is to control the visibility of the cartridge along
with its motion, so that it disappears after it flies a few feet.  Again you can use
either DP or an animated pose to switch the visibility off at an appropriate moment
in the timeline.

You can use erc in Poser 5 and up but it means editing the cr2 file.
Since you have a trigger dial , you simply use it as the master and add code to the hammer part to slave it to the trigger .

Heres an erc document that explains how. http://www.atlantis23.com/erc_download.html

its not as hard as it looks. 

The cartridge , if a seperate prop, could be parented to the ejector rod, you can then animate it individually as needed.

Thank you both for the suggestions.
I'll be looking into the erc code for the trigger/hammer for sure.
I really can't parent the empty to the ejector rod since the cylinder chamber has to be rotated to line up with the rod.
Yes, what I'm attempting is complicated .
My vision is to cock hammer, have it advance cylinder to next chamber,probably not feasible
Squeeze trigger and have hammer fall, that has been addressed
Move ejector rod back and eject cartridge, apparently not an easy task.

you can use erc for that part as well. A master dial for the cylinder rotation and move the casing, and another dial to move the ejection rod , and move the casing out . The two master dials already exist  so its just the slave code you need.  it would be a little easier if the casing was part of the gun. You could then make it invisible and use a prop fo it to be removed completely.

The rotate cylinder while cocking the gun is not hard. keeping the movement isolated to stop it moving the other way when the hammer falls might be.

If you have Poser 8 the dependant parameters might be easier than erc.  
 

Very interesting concept, thank you.
Yes I did dl the erc info. Now to read and understand.
Unfortunately I don't have P8. P7 but use very little. Still enjoy P4pp.

ik, I dint know how erc is handled in P4pp, but its worth a try.

there is also an advanced information on erc http://www.atlantis23.com/arc_download.html

that gets into some pretty advanced setups but may be worth a read. 

The Ruger is looking nice.

Using the hammer cocking action to rotate the cylinder isn't a bad idea but from my tests I didn't see any real gain from using the trigger to drop the hammer. I can probably find one of my test files that has the master and slave coding for the trigger and hammer if that will help.

If you remember I used ERC to eject the shells on the Holland double rifle so that CR2 might give you a starting point.

I made the shells part of the figure though, parented them to the ejector and drove the action with the barrel break and built in a delay so a little different from what you want to do. Still it might be useful to look at in conjunction with the ERC info you DL'ed.

Give me a shout if I can help you out on this one.

Progress report:
I now have the trigger/hammer function working. Thank you ockham for your ercBuilder script it worked like a charm.
I know there is no real benefit for the feature but I'm trying to get the revolver to function as closely to the original as I can.

Now to investigate  markshum's suggestion.

@bob1965
Thank you for the compliment and offer of help.
I believe I have you Holland so will look at the cr2.

@ markschum
You are right about the cylinder moving back when fired. I can cock and rotate, fire and the cylinder moves back slightly. I don't know if I can call the cylinder from the trigger and change the min/max value to 0. Who knows, it might work.

More progress:
Everything is kind of sort of working now. I have to use a pose file to set the cylinder to the correct position then I can use the ejector rod to push the shell out.
Have to tighten up some parameters and solve the cylinder return problem then get someone to test. BTW this will be a freebie :)