I've been scribbling ideas for a new prop. But I also learned that one of my theaters is doing "Mockingbird" this season, and are already having questions about how they are going to do the gun.
I've done this once; for "Tis Pity..." the actor had a plastic gun and a keyfob transmitter in his pocket. He'd press the button while miming firing the gun, and the sound played out the sound system. Which is how I ended up cleaning stage blood out of a radio transmitter but anyhow.
The idea I meant to throw together was basically a cut-down Nintendo Power Glove. One flex sensor in a fingerless glove (or a flesh-colored finger cot) leading back to a XBee or similar radio transmitter.
This does have the advantage of simplicity. XBee modules have onboard analog to digital converters, and can stream a steady set of samples from the sensor. On the other side, a simple carrier allows you to bring the serial data stream into software via a USB cable. This is what I did to interpret the accelerometer data when I was messing around with a spell-casting wrist band. Since the parsing is done on the host computer, you can display the real-time data from the sensor, log it, look for patterns, adjust limits on the fly.
The downside is cost and battery life. The XBee pro is $50, and to make the sensor really responsive you have to be transmitting almost constantly.
But I realized yesterday, as I sat in a brush-up rehearsal of someone else's show scribbling away on notes on my laptop, the trigger finger sensor may not work.
The problem is recoil.
There's been a steady effort to simulate recoil in game controllers and laser tag guns. I'd been looking at those options that very day, towards the prop I mentioned above. On stage, it is frequently done that the actor will jerk the gun in their hands to try to simulate the kick of a real round. It isn't that realistic, but it is better than nothing (blanks, of course, have very little kick either).
This is the way in which the sounds don't coordinate. You can't exactly see the actor's trigger finger from forty feet away, but you do notice if they jerk the gun; auditory reaction time is on the order of .2 seconds, plus they do actually have to pull -- in a 1980's study, it was a full .5 seconds before a forefinger could be brought down on a button. Using a vibration motor instead of an alerting sound brought it down to .4 seconds.
Obviously, if it is too disruptive to tear open a rented prop gun and insert a sensor (the reason why I've been designing a sensor that is worn by the actor instead), it is way too much effort to put a recoil device on. Especially since the best commercial recoil devices are just about up to delivering a satisfying "kick" to the user -- they don't jerk the gun enough so anyone would notice it from stage distance!
Which leaves us back with the poor actor having to coordinate jerking the weapon back at the same time they operate a button. And because simulating a firearm recoil requires such a strong muscular effort, it probably precludes doing anything subtle and controlled with the same hand (like operating a button, or even like pulling a trigger). Which means you might as well have a key fob in the pocket.
But I may be overthinking this. The problem is that I shoot. The kinesthetics are clear in my mind; you grip the weapon securely, and you ease down the trigger. After you've taken out the slack, that last bit of squeeze is timed to happen just as you are on a resting breath, and the bobbing sights are properly aligned.
As an actor, though, what could I make work? Jerking seems natural, and controlled. Perhaps an accelerometer is what is called for. Assuming I can discriminate the desired motion. Pressing any kind of button or trigger feels wrong to me...but at the moment I'm trying to work this out with a hot glue gun.
Maybe I should build that prop after all. Or run across the street for one of those NERF guns I've had an eye on for my next repaint...