The SPAR16's sight's aren't properly zeroed. Especially evident at and beyond 300m, the sights aren't pointing to where the bullet drops to or where the cursor points. With a 300m zero, you have to aim at or above head level in order to hit a 300m distance man sized target in the legs or torso. In order to bisect the target and still hit it near the center at 300m, setting the zero to 500m has worked best for me. I'm using the SPAR16S (with the longer barrel) which will have a slightly flatter trajectory than the shorter barreled standard SPAR16 carbine. Other weapons like the EMR1 don't have this problem.
Example in the video : https://www.youtube.com/watch?v=igIwGDB0_To