Smartchoke does not work + Receiver mod does not work on all SRs

The interesting thing is that accuracy (which seems to be basically the same stat as spread reduction) seems to work with a Scattershot.

When using turbocharge (accuracy, stability) the aiming sights (no aim and aim) get noticably smaller. With the other shotguns they keep the same.

For that accuracy seems to effect the first shot mainly and possibly not in all cases if you are aiming down the sights (e. g. using a scope), if the sights borders relate directly to a weapons accuracy. It does look as if the weapon spread will always be inbetween those borders, but there seems to be some kind of maximum spread that is not effected by accuracy. Using for example an assault rifle the maximum full auto spread will stay the same regardless of accuracy (every following shot might lower the weapons accuracy stat down a minimum value), which basically might make accuracy a pretty lackluster stat on a lot of weapons (sniper rifles don't seem to have less accuracy when scoped regardless of base stat, auto weapons will always get to their minimum accuracy quite fast)