The fluff text about the PPC (taken from http://www.sarna.net/wiki/PPC) says (emphasis mine):
"The Particle Projector Cannon (or PPC) is a unique energy weapon. PPCs fire a concentrated stream of protons or ions at a target [...] The ion beam also extends to much farther ranges than autocannon fire".
It's clearly meant to be a beam weapon, the article at sarna.net even have this nice illustration with the caption "PPC fired by Timber Wolf - notice characteristic helix around the stream of particles":

So my proposal is that you redesign the PPC as a beam weapon, placing it mechanics-wise back in the energy weapon category where it belongs.