snap and auto shot ranges are properties of weapons. If you use the option, it looks into the ruleset to find what the ranges are (or defaults to the values you stated). The easiest way, if a bit time consuming, is to create a mod that changes the snapRange and autoRange of weapons to your desired values. Something like:
items:
- type: STR_RIFLE
snapRange: 20
autoRange: 10
- type: STR_PISTOL
snapRange: 20
autoRange: 10
repeat for every weapon.