Black Heritage Gun?

[Choco Latte]

I've picked up the heritage gun from Karl's Bay like around 18 times or so already and they have all been the sparkly violet variant. I've done some searching online and it seems like some other players have had this problem as well albeit with no definitive explanation or solution (other than getting a Juliana to drop one). I've tried killing 3 visionaries and changing the loop stress to no avail.

Is this a bug? Does it just have a very low drop rate?

[im lazy]

I have gotten a black heritage gun from Karl's Bay night before, might just be a bug.