Did a random TFO and got a ground borg. I switched to my tommy gun to try it out on them after doing the first few I started to get the green tag above their head saying Immune. I switched to shotgun and same deal after a while.
I think I still did Dmg but when I went full auto mowed them down but when had they had green tag didnt go so well also had 4 other people in the run as well.
I did shoot 60 borg for the Endev on the battle zone planet Defia, Defea, Def-somthing and not once I had to remod the tommy and full auto was pretty much one shotting them.