Is there possibility of CH when using AP equivalence vs Inf targets? I remember a rule not allowing CH in this case but no way to find it..
That is perfectly ok.
This tactic may be of use if you want to root out Pillboxes when they are very difficult to approach by friendly infantry but the enemy within is incapable of doing much against tanks. In such a case, the tank may just drive up ADJACENT to the Pillbox hex and fire AP at it. Per B30.35, the neither CA, NCA Pillbox Modifier nor TEM applies if your gun is not minuscule:
"B30.35 AP: Neither the CA nor the NCA Defense Modification nor other TEM applies to an AP/APCR/APDS attack against a pillbox/its-contents, provided the Basic TK# of that ammo type being fired is > twice the Defense Modification that would otherwise apply. An AP/APCR/APDS hit on a pillbox is resolved using the normal HE-Equivalency rules (C8.31)."
At double point blank range with a -2 Acquisition firing on the ITT, your chances of hitting the PB-occupants are very good with 2 flat shots (and maybe Multiple Hits). Your chances of getting a CH are surprisingly good under these circumstances as well: You need to roll less than half of the Modified TH# (which is 8), however, Firer Based modifiers are -4 (Double Point Blank and Double AQ). So if I got it right, you'd get a CH on a Final DR of a 7 or less (!). The AP CH is then calculated as per HE equivalency, i.e. 2 doubled to 4 for guns 37mm or greater. Note B30.35, though.
Per the following Q&A, if you get a CH, the Pillbox TEM is not reversed:
B30.112, B30.35, & C3.71
Question:
A gun fires at a Pillbox through the CA (B30.112) using AP (B30.35) and scores a CH. What is the reversed TEM (C3.71) that would apply to the IFT resolution of that CH?
Answer:
The TEM to reverse is the TEM used, zero.
Question:
For general CH application, is the reversed TEM of C3.71 always that TEM that applied to the shot that resulted in the CH?
Answer:
In this case, that is the case.
Bottom line:
Your chances with an AFV might be no too bad, to score a 4 flat vs. the occupants of an otherwise impervious Pillbox.
von Marwitz