With the ruling in
this thread it seems a few errata are in order to make things clearer.
I gave a wrong page reference for the problematic section of A Time of War but page 186 offers this:
Tactical Armor vs. Internal Structure: These rules also
consider a tactical unit’s internal structure identical to tactical
armor. Unless the unit is a battle armor suit (see below) or its
design notes state otherwise, the BAR value for any tactical
unit’s internal structure is presumed to be identical to that of its
exterior armor.
This is mostly troublesome because of Tactical Operations page 338 which offers this:
Game Rules: Rifles lack the power to function effectively at normal space-to-space ranges, but may be employed by aerospace units operating in atmosphere and their
ground-based counterparts, where they function as normal direct-fire ballistic weapons. However, because they lack the armor-penetrating power of modern autocannons,
rifles of all sizes must subtract 3 points of damage (to a minimum of 0) for successful attacks against any unit except for conventional infantry, battle armor, ’Mechs using
Commercial Armor, or Support Vehicles with a BAR rating below 8.
The easy answer would be to self-contain A Time of War page 186, which seems to be the intent but because of page 212:
VEHICULAR WEAPON TRAITS
All vehicular weapons—also called heavy weapons in Total
Warfare—are classified by various codes that indicate their
unique traits in combat. These weapons perform per their normal
Total Warfare-style rules when fired at opposing vehicular units,
but against infantry units in tactical combat, these weapon traits
(described on p. 113 in Total Warfare and shown in the equipment
tables on pp. 303-305 of that book) yield alternative features that
replace the normal anti-infantry effects in Total Warfare.
And the rule section quoted above saying unit with no mention of ignoring the -3 for internal structure or against buildings and it does get a bit confusing.
Then we have Penetrating Critical Hits:
DAMAGE
Support Vehicles handle damage differently than Combat
Vehicles. Every time a Support Vehicle suffers a hit that exceeds
its BAR rating, a chance exists for a critical hit (called a penetrating critical hit), even if armor remains in that location. Penetrating
critical hits are rolled in the same fashion as standard critical hits
(see Critical Damage p. 192), with the following exceptions.
I'll skip to the next problematic wording:
Penetrating critical hits may occur in addition to any normal
critical hits due to location or internal structure damage. The
Armored Chassis modification does not affect rolls for these
normal critical hits.
The underlined section in the first quote is frankly a weird way to word things if Internal Structure does not have a BAR of it's own and if Penetrating Criticals are only to be checked as long as Armor exists to provide even partial protection.
The second quoted section seems to back that Penetrating Criticals are check for in addition to Internal Structure damage.
So the easiest way to handle all this would be adding a few lines to Rifle Cannons about the exceptions to the -3 damage modifier for Internal Structure, Buildings, Terrain, any other valid targets not already listed that I might be forgetting, and exploding for full damage with a second errata to Total Warfare to make it clearer that Penetrating Critical Hits are only checked for as long as Armor exists in the location struck.
A Time of war page 186 would still be a bit confusing but like I said the intention seems to be for it to be self contained to A Time of War so I'm not sure how to fix it but because with the above changes it probably could be left as is for now especially as it only causes problems in a few specific cases(Rifle Cannons, possibly Mine Clearance, and I'm probably forgetting another).
That should also neatly solve my pending question about Patchwork Armor as it would make it entirely about the armor.