found a couple bugs with guns

the raptor and gilded griffin deal neutral damage to vanaduke, as if I had shot a slag walker (I mean the PIERCE damage is neutral to him, not the bonus)
(this has probably been said before) the magnus charge attacks push enemies backwards to where theyre facing (shooting one in the back pushes it towards you)
the magnus problem I can get around but really, the raptor doesnt even deal the correct damage to the enemy I got it for
edit: fixed it so people who skim over it will understand, added gilded griffin

nope
I mean as in pierce should have the numbers as if I shot something weak to it
so not the fiend damage bonus not working, its that the piercing damage is doing neutral to him
that correction you made doesnt do anything

Oh whoops I misunderstood sorry about that.
And now that I've reread your problem that's a big error.

updated the OP with gilded griffin, tested it and found the same issue
poopsie, it shows white colored numbers but it deals as if it was effective damage, I used to own a blitz, I saw how it worked

blitz needle also has the same "neutral" damage numbers to vanaduke, because hmm....
you may want to read this -> http://forums.spiralknights.com/en/node/79394#comment-696958

The Magnus bug can lead to some interesting strategies.
Being able to reposition your enemy this way is unique.
Unfortunately Vanaduke is not affected by Fiend bonus UVs
From http://wiki.spiralknights.com/Vanaduke
"While considered a Fiend, he has unique damage resistance: he is slightly weak to Piercing, slightly resistant to Elemental, and neutral to Shadow until his final phase where he gains complete immunity to Shadow. In addition, he does not take additional damage from Fiend damage bonus UVs."