Well shooting just won't do much against them.
What you need to do is get into combat very fast so they don't shoot you to pieces before you get there.
I would recommend Adrenal glands to up your Inititive, Extended Carapace so the holy bolter won't blow holes in the bugs.
Leaping is a must have, it means you don't get rapid fired and you'll nearly always start combat with one extra attack.
Now to the weapons.
Rending Claws and Scything Talons.
They're the most effective way of taking down guys in armour and if your opponent decides to take a tank the warriors will still be able do damage it due to the Rending Claws.
There's your 38 point marine killer.
Be midful of the Necrons as I'm sure you know they have a nasty habit of teleporting all over the field. Most annoying.
