For the P, a pretty good one that I personally run is to leave the 3B arm on, drop the right arm to one with an E-slot (forget which), and run it 2cLPL and 6MG with a balanced load of heat-sinks and ammo (whichever is more comfortable for you, between ammo for the MGs and DHS for the pulses).
It has fantastic punch at range, though hot, and can take a fair bit of armor out quickly before retreating with MASC; the relatively short cLPL beam duration lets you get out and in and poke fairly well while minimizing exposure to return fire during the early trades of the match.
Once people are opened up, those 6cMGs make utter MINCEMEAT of internals. Anything big like a Gauss or AC/20 is going to be gone in a heartbeat. It's just ferocious, probably one of the few viable MG builds. It's like the similar IS Jager build on steroids, in a chassis much smaller, faster, and more maneuverable.
Woe betide the enemy that you sneak up on undetected, for the immediate application of extreme wubs and MG fire to thin rear armor is going to ruin somebody's day in a bloody hurry.
Edited by GroxGlitch, 09 October 2015 - 11:11 PM.