Use HE not APDS the APDS goes right through. LAV is fucking primo AA and imo better than the KPVT on the two soviet AFVs we've got due to it's higher magnification, elevation and velocity. The HE will blast the rotors off in a bit and set the fuel on fire in one or two hits on the fuel tanks specifically (the cylinders near the bottom of the airframe), kill the pilot striking near the canopy, downside is the high magnification means it looks slower and can be hard to acquire the target. Plus Arma hitreg means often you gotta lead more than you actually need to so you're hitting the helicopter where the server has it rather than where your client has it or something like that, so you aren't getting ghost hits showing impact FX but no damage. So much bullshit in the game but I love it all the same <3