This mod adds 2 settings for every ammo-turret, car, cargo-wagon, fluid-wagon and locomotive from my mods.
Both can be set to 1-100%.
One adjusts the entities hp, one its resistances.
This gives you the possibility to down-balance as your heart desires.
Both settings at 100:
Car X has 1000 HP and a decrease-resistance of 5 and percent-resistance of 10.
HP-setting at 20 and Resistance-setting at 50:
Car X has 200 HP and a decrease-resistance of 2.5 and percent-resistance of 5.
How resistances are calculated can be seen here: https://wiki.factorio.com/Damage#Resistance