Just noticed that the Assault Carbine has 20 base damage and the GRA Assault Carbine has 16 base damage and lower DPS? Is that normal?

If you have the Grunt perk that would be why. They forget to add the GRA Carbine to the list of weapons affected by that perk.

It's because of the Grunt perk not applying to GRA weapons

oh that's pretty lame and/or lazy... think they'll fix it?