Why? ???
Why? Well not for the official but for the house rule - the SnubNoose or Plasma Cannon instead of the PPC makes perfect sense for the Manticore and Myrmidon
Its a Parti-Kill and by the description of the Parti-Kill in the TRO3026... it sounds like a Plasma Gun - instead of lobbing heavy ions with hypervelocity it lobs a huge chunk of confined (however) plasma much slower and of course at shorter ranges.
And because I lost my sanity some years ago already:
in the left side are the 4 PPC models I made half a year ago: up-down Donal, Parti-Kill (the other both are proxies)
Sure both similar massive but on this model, the Parti-Kill is already equipped with armor and heat-sinks (reminds me that I need to finish the Manticore)