This build began life as Blagg Zear's JM6-S Laser-Mech which I enjoyed, but I found myself increasingly acting as a sniper and wanted more range. I'm really starting to like this one and it goes well with my current playstyle. And now for the prerequisite bragging screenshot:
I have practically the same build I am planning on trying, minus a ton of machine gun ammo and plus a BAP. I'm happy to find someone endorsing it. It's similar to the "molten steel" builds, but no XL engine. I feel that my XL Jagers go down too easy in a brawl.
I used a dual ER PPC on the JM6-DD "Big Troll" for a while but I had found that the heat was not manageable after the increase to 15 heat per shot. I usually aim to get heat efficiency in the mid-30% range so 27% is a little low. If the ERPPCs weren't thermonuclear reactors, I'd go with them but unfortunately that's not the case *right now*. Also, when using a lower rated engine (sub ~300) the machine guns aren't of too much use on the Jager. Not a bad build but not exactly optimal. If the extended range of the ER's is not desired, swapping to regular PPCs and throwing in a faster engine is, IMO, the way to go. With a larger engine you can throw heat sinks into the engine and put on Ferro armor too. I call this guy the "Lesser Troll" or "Ogre" as a reference to the "Big Troll". I've had good luck in the few times I've used it.