The main idea here its simple. Oneshot any enemy that you can kill with a songle slug headshot, if the enemy its heavy armored, a single bucketshot will proc enough viral and heat to actually kill it with a single slugshot after that. Its aimed mainly as an endgame build geared towards steel path, if using a 100% armor stripping frame, then replace the dual stat mods with flad elemental damage ones.
Agains corpus do magnetic + toxin. Usually toxin its enough by itself, but against some specific units that are toxin damage immune you want to have magnetic damage to actualy take down the shield and vruteforce kill them.