In lvl 50 pvp I notice no difference between the plasma cell and the armor piercing for damage. With the armor piercing cell supposedly penetrating armor an additional 35% one would thing it would treat the attacks as if they have 35% less armor. I havent seen this as being the case. It doesnt say what it does on the character sheet nor does it seem to come into play at all in pvp. So if someone could explain how this works I would be interested in hearing it. Grav round I have seen a difference but the cell,not at all.
This is where you can upload your combat logs and examine the numbers:
Yes it does bypass 35% of armour, no 35% of armour does not mean 35% more damage.
Means about 5-8% more damage depending on how much armour the target had in the first place (light, medium, heavy).
Examine other energy/kinetic attacks (white damage) and you'll see the difference on a parser if you do the attacks enough times for a good sample.
Mortar volley for example is a kinetic attack.
It works as it is meant to.
Your real damage booster is not armour pen but stacks and procs generated by grav rounds to high impact bolt, demo round and above all, full auto.