Yep, a side effect of the invisible, no damage bullet. Sometimes it will also cause them to sway backwards violently.

I have decided to try to make a mod version of this with a more true-to-life GUI interface. Going to take my sweet time on it though. It's been a long time since I've done any 3D modeling or texturing, and I'm not much of an artist. Plus I have to figure out how I can create a dynamically moving reticle based on the ranging... I know it can be done; there's a lovely version of the XM-25 for VBS2, according to YouTube videos.
I think the scripting won't be too hard though. Most of what is complex in it now is simply workarounds for having to use scripts instead of a mod.
I will release the scripts version, limitations and all, for anyone to use in few weeks after it has seen a little more testing and refinement on the server. As of right now it's working peachy-keen though, but new issues could crop up in different mission scenarios.