if enables you hear the shot and see the railtrail imediatle after you pressed fire, otherweise the game wait s on the server to confirm. something like this
It really doesn't matter at all, it's only a visual thing. Whether it's set to 1 or 0 your shot is still in the exact same spot, you can't change that. It's like how Nukm said it.
I use 0 and have been doing since I first set up my QL config in like 2009 when linkooo told me having it off its better. I have 70+ ping best case scenario and it feels fine. Also felt fine on lan, if there is one weapon thats not affected a lot by ping its the rail-gun. I just noticed that this post is completely pointless and lacks any objective value, sry bout that.
#4 cl_timenudge -20 / cg_predictlocalrailshots 1= no delay + near correct rail position (enemies appear laggy)
The best combination depends on the person. I use #1, the timenudge -12 does not fully make my enemies warp + I have no delay on the shot = perfect rail feeling.