I have all guns via drops. But I will agree with the theory in principle. I've received over 10 suros and gjallerhorns but I got my Red Death dropped a few weeks ago for the fist time. So Id totally believe that some guns are "set" to drop for certain players more than others. Like I've got one TL and I have a buddy I play with that has gotten several in a row on nightfalls. So maybe in his "spot" for increased drop rates is the TL while mine is the Suros?! Could be.