(Answered UPDATED) Critical Rolls/Hits transfer

[ApolloAndy]

What exactly does this rule mean and when does it apply?

My initial reading is that if you hit a mech's LA with 14 internal and no armor with an ER PPC (clan) there's a chance you can get a roll of 12 and get 3 critical rolls against the LT, even if the LT hasn't been damaged at all, but that doesn't seem like it should be right.

[Xotl]

You're kinda right, and kinda wrong.

If, at the start of the phase, a Location does not have any critical components in it that can take any damage, any critical damage done in that phase will transfer to the next location. To use your example, let's suppose that both the Shoulder and Upper Arm actuator took critical damage in prior turns, and there's nothing else in there save Endo Steel. You would roll Determine Critical Hits, and if you get anything, those Criticals would get resolved in the Left Torso.

However, the "12" result for the arm does *not* transfer: you're not rolling Determine Criticals in the Left Torso, you're rolling it in the Left Arm, so you resolve the 12 result, which is limb blown off. A limb with 0 internals left, so it can't be used as a club, but the Left Torso at least does not suffer Critical damage.

I don't think I've ever seen that happen.

[Xotl]

Please note that we're changing our answer here.  The previous answer ignored the existence of the "Destroyed Location" rule on TW page 124 (easy enough to do, because it's not represented on the Step-By-Step damage process on pages 122-123, and is separated from those rules by a page or two).

The new ruling, currently in print in the new BattleMech Manual and to be entered into TW errata, is as follows:

When a location is destroyed, rather than just damaged, no check for critical hits in that location is made unless it contains one or more explosive slots. In that case, any resulting critical hits that strike explosive slots in that location are resolved as normal; hits that do not are always discarded without transferring.

In other words, you check for crits if you damage a location, but not if you destroy it, unless when it is destroyed it has ammo in it.  Even then, any crits that result never transfer.

In terms of the specific scenario given in the original post, there would be a check for criticals in the left arm if and only if the left arm had ammo in it.  If it did, make a crit check, but any crits that result could only hit the ammo in that arm; any of these that do not strike ammo are discarded without exception.  There would be no check for crits in the left torso.