What happened? M551 using the M409A1 shell damage

I’m using the M551 (8.3) and having a bit of a tough time with it… I finally get a broadside hit on a Rochev (Israeli 6.3) using the M409A1 shell with almost 4kg TNT equivalent… it was a straight shot, no angle… at like 50 yards… textbook broadside… and all I got was a ‘hit’… then an Ostwind killed it… What happened? The shell go through without detonating?

M409A1 is the HEAT one, no?

If so, thats just how HEAT shells are.

Self propelled artillery can be usually 50caled from side from my experience.

Or use HE shell if you have chance to reload it.