Depending on who's between whom... Follow me here.
You shoot at the guy your PhysAd is punching, and the target is between you and the PhysAd. You hit him, but it glitches, so it's a "through and through" shot, hitting your PhysAd as well. But, fortunately for your PhysAd, you have to take into account the target's Armor + Body as extra armor before it hits the PhysAd. That way, he can get hit, but it won't be that threatening unless both he and target aren't wearing armor...