What you want to look at isn't so much the damage amount or AP .. those are good as default. It's the min/max radius that you want to look at. These settings decide how much damage is capable of being done from the initial explosion point.
An example :
In sh5 stock : min max of standard dc barrel = 2m and 4m
In GWX sh3 : min max of standard dc barrel = 4.5m and 40m
So change the damage back to normal and try the different min/max radius .. you'll be happy with the result .. unless you die
