Sources: Total Warfare (TW), 9th printing PDF. TechManual (TM), 6th printing PDF.
On TW page 142, there is a heading for "Attacks by SRM Infantry" under Special Munitions - Infernos. This gives rules for conventional infantry (CI) with SRMs making attacks with Inferno ammo. While the rules for resolving the attack are clear, it remains somewhat unclear how you declare that said infantry have access to said munitions, especially since CI don't normally track ammo. How exactly does this work?
Possible options from my perspective:
1a. A standard SRM squad/platoon (as found on TW page 213) is declared to be using Inferno ammo instead of Standard ammo at the start of the fight, similarly to how other special munitions are declared (as described on TW page 140), and the squad/platoon uses the Inferno rules throughout the fight. Optionally, this may also be possible for custom CI platoons constructed using the TechManual construction rules and any of the SRM Launcher support weapons (see TM page 352).
1b. Similar to 1a, except that the use of Standard or Inferno ammo can be freely declared turn-by-turn during a fight (due to CI not tracking ammo in detail).
Either of the above options seems reasonable, particularly in light of the fact that the TW rules predate the release of the TM CI construction rules, but the existence of SRM launchers explicitly having "Inferno Ammo" (and doing less damage than "Non-Inferno Ammo") in TM confuses things somewhat. This therefore creates another possible option:
2. CI platoons
must be constructed using the TM "Inferno Ammo" SRM launchers in order to use the TW Infernos rules (possibly meaning that such units will
only be able to use the CI Inferno rules, and will be unable to make standard CI attacks, e.g. should they wish to do damage to a mech rather than heat, they will be out of luck). This option is a bit odd, since it departs from how the "Inferno ammo" generally works for other CI weapons (granting the CI "F" tag in exchange for somewhat reduced damage), but
not using this option means there is little reason to ever use the SRM launchers with Inferno Ammo in construction, since the standard ammo deals more damage and could still be converted to Infernos if desired. Given that either way is a bit weird, it is probably best to pick one and stick with it.
Clearly, a rules committee decision is required here. What would you choose?
Edit: These questions are highly related to the TechManual-based questions in
this thread; both can likely be answered together.