The october patch introduced a raise to the ERPPC ghost heat limit for the NSR-9J, so it can do the ERPPC+GR sniping from its stock build better. Here's an upgrade to the stock. XL alt: LE alt
Don't own the mech yet, but I imagine it will be one of the strongest snipers. I mostly built it to make use of the new ERPPC ghost heat quirk.
Real man Skilled players whom are good at aiming should not rely on ML as backup weapons because Gauss + hand actuators are an hard counter for any brawling light. For this reason, fitting the biggest engine available for best speed and pokes and play accordingly to their role seems the best solution. Still, projectile convergence will be atrocious on longer ranges. EDIT: or fit a LE325 and fit a TC4 for increased projectile speed and zoom