What weakness period? It's either got 75% damage resistance or it's firing.
Yeah, in case you are not experienced with how to properly counter emplacements, first you force brace, then pull back and 30 seconds later you come back and nuke it.
Retreating units do not drop weapons on the ground and wait around until they get new ones, neither emplacement crew should reread the instruction on how to operate the weapon after ducking for a minute.