Let's try this again. :)
Any burst-fire weapon available to BA but not listed on the "Battle Armour" table on p. 217 (such as the small pulse laser) defaults to the burst-fire damage listed on the "BattleMechs, ProtoMechs and Vehicles" table (in the case of the small pulse laser, this would be 2d6 damage).
Basically, first check the Batle Armor table. If the weapon you're using is there, then you're good. If it isn't, then move up to the BattleMechs, ProtoMechs and Vehicles table and use what's written there.