Sounds like you're trying to fire a lot of mass at high speed.
The way cortex command does weapon recoil means that you get a proportional impulse to what you fired, so if we consider impulse to be change in momentum, and momentum = mass * velocity, when you fire a heavy particle quickly you get a very large impulse on the actor firing it, which will, in this case, splatter the actor across the map.

Make an invisible MOSRot which shoots (via an attached AEmitter) said superfast superdense bullet. The MOSRot should be fired at a slower speed and has lighter weight than the round it's supposed to shoot out.