selfquote from another thread:
The BLR 1G was my first own Mech to really play with.
I used to run it with an LRM 20, 5 MLs and two AC2.
This build is a straight improvement, I cut down on the LRMs due to the tube size but gained a Large Laser. The AC5s really shine as you can pump out lots of DPS with them and you will
cool down while doing so, which matches very well with the laser arsenal.
Little downside is, you´ll probably need four weapon groups to manage the weapons.
In general I´d say that Battlemasters do best with high mobility, which means a big engine. They arent really tanky, especially not with an XL Engine, but your agility allows you to use cover and pop out at places which are really uncomfortable for the enemy. Your high torso energy mounts allow you to shot over hills with ease (seriously, they are about cockpit-high) or you can just stick your left arm out for some heavy ballistic fire. The Mech is best played, as others said, a super-heavy skirmisher and a flanker.
Avoid prolonged uncovered firefights because this energy-heavy Mech runs hot at some point. When enemy attention is focused elsewhere, pop out and bring in the pain.