Myattus

WoW! You even fixed Override Bones with IK too....and within minutes of posting an issue! This is the best customer service I have ever experienced! Youve saved me so much work! With immense gratitude, thank you so much.

As Mike mentioned, there are actions to override the animation in the C2 plugin.  They're under the Override Animation section in the Add Action dialog, They're pretty straightforward.  
The Override Object Animation action is the more simple of the two.  
 In your case you most likely want to change the angle of the forearm bone, or if you're not using bones, the forearm sprite.
You specify the object name from Spriter for the bone or sprite you want to change.
Specify the component (x,y,angle,x scale, etc) you want to override.  In this case, angle.
Then you set a new value, like 45, if you want it at a 45 degree angle.  You would have to figure out whatever math you wanted to use to decide what angle for any given moment.

The Override Bones With IK action does IK that is the equivalent of holding shift while changing the angle of a child bone in Spriter.
For the action, you specify the name of the child and parent bone you want to apply the IK to.  Then you give a target - where the IK joint should reach to.  In Spriter this is where your mouse pointer is when doing this type of IK.  Again, you'd have to figure out the math you wanted to use to decide where the IK target would be for any part of the recoil.

You probably won't need the last parameter,Additional child bone length, for your purposes.   This is if you want to extend (or negative to reduce) the length of the child bone.  This is useful in cases where the tip of the bone in Spriter isn't exactly the point that should be reaching for the target.


Let me know if you have any questions.

There might be possible options, both pretty darned complicated.
There is a way to override the animations control over sprites or bones so they can be controlled in real-time by C2, but I've honestly never used that feature myself. I'll bring this thread to Edgar (Spriter's programmer and the creator of the C2 plugin) to see if he can link you to further info.

Aside from that option, yes, you could separate the upper body or just the arm in Spriter to be a separate Spriter object, then anchor it to the character sprite, synchronize animations, and then add recoil animations... this option would be very time consuming, first to break up the character and their arm into separate Spriter files, then to properly event everything to stick the arm to the character Spriter object and properly synchronize everything.