http://mwo.smurfy-net.de/mechlab#i=119&l=571d39e6c2427e0b96f9b7a1e3c7dab0af8b8aae My first build that I've posted. I have had good luck with this so far. The armor is a little light on the legs but it's worth it to have 5 tons of ammo. The standard engine also let me put on Ferro-Fibrous and Endo-Steel.
I've corrected this to the proper naming convention used on the site since you are still new here The next time there shall be trouble!
IMO the STD355 engine is a weird one and you have too little AC5 ammo. Since it comes with a STD340 I think I can make this into something pretty and cheap My edit: http://mwo.smurfy-net.de/mechlab#i=119&l=980fa599de7b6abeae95deab3d9018e67637882c
I run my heavy metal with 120 shots of AC/5 ammo and I don't run out until the end of the match. 210 seems a bit much for only 2 AC/5's.
You can swap 1 ton of ammo for an ML if that's your preference. I run a TDR-5S with 2xAC5, ERLL and 3ML. 150 is too few so 180 at least, 210 if you or an enemy are really good at staying alive. This build seems to be mostly to snipe from range rather than using the MLs as your main weapon, and rightfully so since the Battlemaster is pretty cumbersome in brawls compared to a heavy, and with only 4 MLs and a double AC5 many heavies will outgun it.
In the 1D, firepower is king before speed. I run the 1xERLLas, 4xMLas, 3xAC/2, 275, CASE version of the Clawmaster because it's the best 1D build I can afford. It's a big, slow, angry fortress of a 'mech (and it works hilariously well when paired with a dakkajager).