(Originally posted this issue to the Mod forum, but without much sucess. As it is largely a GECK question, it probably better belongs here.)

I am trying to create a non-VATS version of the sniper (and gunfighter, Commanado) Perk so that instead of increasing VATS hit percentage, it lowers drift.
I tried changing the function "Calculate To Hit Chance (x1.25)" to "Calculate Gun Spread (x.75)".
I believed that instead of adding a plus 25% chance of hitting in VATS, this should decrease the spread by 25%, thus increasing the chance to hit when using the defined weapon.

Unfortunately, it doesnt seem to have any noticeable difference on the spread.

Any ideas what I am doing wrong, and/or suggestions on how to fix it?

I was under the impression that gun spread was affecting directly by, and only by, your gun skill with that gun, and the global variable. So changing it would require you to increase skill, also increasing damage, or the global variable, thus affecting all weapons for everyone. But I guess I am wrong if you can affect it otherwise. >.>

Spread is determined by the spread variable on each gun, and also the standard "auto-aim" that your player immediately has configured will always cause an up sweep on the round. So the first best thing to do is to disable that auto-aim so bullets will go straight not up. Then after that you have to some how affect the weapons spread factor but only for the player. Not sure how to do that.

Auto aim isn't a problem. I have that sorted.
The spread is controled both on the weapon and in a number of values (mainly the FGunSpread... ones) in the Game settings. I have already tweaked those to give much closer to real-world accuracy.

The problem is the settings affect all player weapons. Adjusting the values to make sniper rifles anywhere close to realistically stable, would make all weapons extremely accurate, even for low level characters with very low SG skill.
What I am trying to do is make a perk to boost skill with sniper (and other 2-hand rifles) without affecting overall SG skill.

I can set the conditions in the perk settings so it will only apply to these types of weapons, but I'm not sure how best to implement reduction in spread in the form of a Perk.

The "Calculate Gun Spread" function in the Perk settings would seem to be designed to do this. However, as I said earlier, it doesn't seem to have any effect.
I was hoping someone could let me know why this doesn't work, and/or give me some pointers on how to manage this.

Did you try extreme variances in the Calculate Gun Spread Entry point to see if any value made a difference? Like X 0.001 or X 10000 just as a test. Are you 100% sure your conditions on the perk are setup for the player and the gun so the perk would take effect at the proper times?

Lastly. You could create a Base Effect of the script Archetype and then create an Actor Effect that uses the Base Effect, then use that Actor Effect as an ability in the Perk. This way you could apply a script to the player to adjust the spread setting but only have it applied on the player and for specific weapons as defined by the perk conditions.