I just bought 200 of the new deldrimor supply chests that can drop the volcanic weapon boxes. They cost me 4 thousand tyrian defense seals. I got zero volcanic weapon boxes. I've opened another 50 of these boxes previously and got zero as well.
I've opened 250 DRM end chests or more (mostly gold chests from CMs). I've gotten zero volcanic weapon chests from there.
I could understand if it was a rare weapon collection with no mastery point tied to it, but this is a STORY achievement with a mastery point! I haven't gotten a single weapon for this collection, and I have played DRMs a ton!