Is this a known issue?

Well, for start - I never drove a tank IRL or was a gunner in one, but this seems a bit off. Before making any bug report, I'd like to ask is this a known issue:

AP Rounds, T55 - Bouncing off buildings, and sometimes, depending on impact angle, terrain. Screenies below, look for the yellow dot against the sky - that is a round that already bounced. Bounces up, falls down.

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Armor piercing rounds like the SABOT used in US tanks and other types of AP rounds will go right through soft targets and hit the terrain and get deflected. HEAT rounds are best used on soft targets like BMP's and soft structures like buildings. The buildings in DCS aren't modeled like in ARMA either. They have something similar to a 2D hit box area so they can only be destroyed by the correct angle. If you go up to them and shoot machine gun and you see the rounds impacting on the surface and making fire and black smoke you're at the correct angle.

Added: I know you didn't mention ARMA, I was just using it as a comparison on destructible ground objects. Also, I wanted to mention that you're probably seeing the round go through the structure and impact the ground behind it and then deflected up. ED is completely remodeling the Caucus map so maybe we'll see more advanced structure modeling and destruction in the future.

Thank you for the reply and explanation. I don't mind comparison to ARMA, comparison is a simple way to show differences and different concepts without much explanation, and it's not necessarily a way to denigrate any of the sides in the comparison.