(Answered) Indirect fire and firing arcs

[BoyOfSummer]

BMM p. 24 (firing arcs)
BMM p. 30 (indirect fire)

"If an attacker has LOS to its intended target, the attacking player then checks the firing arcs of his ’Mech’s weapons to see which weapons can hit the target." BMM p. 24 (firing arcs)

"Indirect fire allows a ’Mech without a direct line of sight to a target to attack that target. An attacker with valid LOS to a target cannot make an indirect fire attack against that target." BMM p. 30 (indirect fire)

So: my Mech is on one side of a mountain several levels high, an enemy Mech on the other side of the mountain. There is no LOS, but an allied Mech has LOS on the enemy Mech on the other side of the mountain. My Mech has LRMs in the front torsos.

Situation A:
The enemy Mech is in my front firing arc. No doubt, my Mech can indirectly fire its LRMs at the enemy Mech. So the LRMs curve around the mountain or make an arc over the mountain to hit the enemy Mech.

Situation B:
The enemy Mech is in my rear firing arc. Can I fire my LRMs in the front torsos indirectly at the enemy Mech behind the mountain? BMM says that the firing arc is only relevant if there is an LOS (see above), which is not the case here. And the LRMs would always have to make a turn or arc with indirect fire anyway; in this case, the turn or arc is just a bit more... extreme. And a suitable firing arc is not one of the requirements according to BMM p. 30-31.

[Xotl]

That passage doesn't say that firing arc is only relevant if there is LOS; it says as part of the standard firing sequence, after you verify LOS, the next thing you do is check arc.

As stated, indirect fire only waives one requirement: the LOS requirement.  You still need ammunition, you still need to be in range, and you still need to be in arc.  Unless a rule specifically gives you permission to do something, assume you cannot do it.

[BoyOfSummer]

Thank you.

We had played it that way (firing arc matters) because we didn't agree and preferred to stay on the safe side in terms of rules.

But I would have loved to cover this Catapult behind the mountain with more LRMs from my Perseus...