Thanks for posting with pictures, Nate. although I've heard from other people about WD40 leaving a varnish behind or hard coating behind, I've never seen it in over 30 years of use in my gun barrels. It is a sucking lubricant for sure compared to real lubes, but here in this ambient humidity, it works fine as being the only 'oil' in the tube between shooting the gun. Indeed, I've used just WD40 for storage (accidental) of MLs it worked just fine.