C6.5 CASE N; ACQUIRED TARGET: When a Gun (including the MA and SA [Secondary Armament, as per Chapter H Vehicle Listings], of vehicles [EXC: not FT or LATW]) of ≥ 20mm other than a mortar fires at (not Interdicts) a Known unit or a bridge, it may place a " -1 Acquired counter on its target ....
Indeed, only MA ≥ 20mm (see above)Only MA can acquire. See C6.5.