An M3 isn't an empty box. There's stuff inside it. AP [well, not all of it] works not by blowing up once passing through armor, but by punching gigantic holes in things in modern guns. The Abrams tank in use now has an armor piercing round that has no explosive component, it's all kinetic.
The act of an AP round "passing through" the M3 would cause massive damage, and this bug has been around for ages. It really needs to be fixed.
From
Tank Aces by Ralph Zumbro:
First armor v armor Desert Storm
Amazed, we counted 15 holes of differing sizes in I-35, mostly medium to large machine-gun holes with one small-caliber AT weapon of some older type. Luckily most of these rounds either didn't fully penetrate or just didn't hit anything sensitive on the way through.
...but on the way back to the supply-and-resource area, we were engaged by a T-72 and took two main gun SABOT rounds right through the hull. When the first round hit, I was only scared. When the second one hit, that terrified me. After the second round, I knew they had a bead on us and waited for the third.
Miraculously, neither of the two pig-iron SABOT projectiles hit anything sensitive, including human flesh. They just went in one side and out the other, causing only minor flash burns to the crew and their passengers.
Anything is possible....

Why so many excuses?
The m3's side OFTEN bounces AP rounds off, this is inaccurate and should be fixed....simple.
A shot passing through should have the hit sprite like a ricochet, BUT the round shouldn't bounce off, also SIMPLE.
I swear some guys search these threads just hoping to find someone to disagree with.
Good thread dude, 
Not so much excuses as
plausible explanations as why it
could and did happen in real life.
30mm to the wing and the plane flies on? Maybe a dud?
88mm hit doesn't kill the M-3? Maybe the round passed through?
The internet and programming is finicky sometimes. Everything isn't always black and white. With the amount of rounds we fire daily, if in real life, there are bound to be some anomalies.
The percentage is probably very small but it seems like a much greater problem because we are doing it non-stop, 24/7.
wrongway