I don't think infantry can get SPA's? Considering the entire squad/platoon would need it as well.
In Campaign Operations a lot of the SPAs have a unit type of ANY. Some of those actually specify that only certain crew can use the SPA. So, while you wouldn't think infantry can use that SPA there is nothing that says they can't.
MANEUVERING ACE
Unit Type: Any non-infantry
MARKSMAN
Unit Type: Any
The Marksman Ability enables a
MechWarrior, ProtoMech pilot, fighter pilot,
or vehicular crew gunner to...
RANGE MASTER
Unit Type: Any
The Range Master Ability grants the warrior mastery over any...
FOOT CAVALRY
Unit Type: Infantry
This isn't aToW so you don't have to worry that every soldier has it. Not unless you want to track things at that level. Just look a the MANEUVERING ACE SPA above.
Can't use Precision + Caseless IIRC but for standard ACs then I agree.
Especially those long ranged 2's & 5's where the 1/2 shots doesn't hurt you.
Not exactly sure what you are referring to on this but...
A Field Gun platoon can use multiple ammo types. So one gun could have precision, another caseless, a third tracer rounds, and the fourth armor piercing.
If you meant they can't fire both in rapid fire using the same gun... that would be correct. Though a question was asked long ago about pulling multiple ammo types if only 1 shot remained. I don't remember what the official answer was.
If it was meant that UAC or RAC can't use speical ammo... would be also correct so ignore me then.