Lenyoga,
Thanks for testing this!
Yes, increased view distance is needed in the demo mission since the XM500 is a 2 km+ capable weapon. I have updated the instructions to mention the need to set the view distance according to potential target distance (up to 2500 meters).
A weird thing happens in OFP when you fire from the prone position on even the slightest slope. For some reason, the bullets are deflected to the left/right or up/down depending on the angle of the slope relative to the target direction and the severity of the slope. This problem does not happen if you are kneeling or standing and it also does not seem to bother AI units. The user manual does mention this. The sniper duel in "non IGP mode" is very difficult because scope stability is greatly reduced when you are kneeling as opposed to lying prone (to avoid the "slope deflection bug"). If you run over to the wood platforms, you can then fire from the prone position without the “slope deflection bug”. From the wood platform to the snipers are about 1420 meters away, so, while in full zoom, put the 1400 reticule graduation just a little above their heads and you will nail them.
Regarding the lag you experienced when firing the IGHEIAP round, it is because those rounds are guided rounds and require functions and scripts to determine the intended target and then direct the bullet to the target. It is a resource stressing task to make a guided bullet when the game engine never intended guided bullets. Determining the most likely target by analyzing the initial bullet trajectory is especially CPU intensive. I have now uploaded Beta v1.1v1.2 in which I have modified the target search algorithm to reduce the lag and improved the targeting (v1.2). Let me know if you notice a difference.