This is a remix of a model I got from Thingiverse a long time ago. I can't find the original model anymore, but this has been completely redrawn in Fusion360.
The Fusion file is parametric. I've tested it a few different ways and changing the parameters hasn't broken the model yet that I can find.
I've included several pre-meshed trays for various calibers.
The author hasn't provided the model origin yet.