After a current reloading session I was contemplating long term storage possibilities. I did a bit of reading here (this forum) on different bullet and primer waterproofing ideas and suggestions, but I didn't find discussions of a recent vintage. From past endeavors I recalled a way of waterproofing improvised cannon fuse. Smokeless powder is mostly nitrocellulose, a sealant of mostly the same stuff ought to make sense. How to do it, glad you asked. A good quality ping-pong ball is made of a celluloid material, with a molecular structure very much like nitrocellulose. Cut a ping-pong ball into small pieces, and dissolve in acetone. Viola, nitrocellulose lacquer. For a dissolving vessel, I used a 1/2 inch copper plumbing cap, the same kind you solder onto water lines. (Safety Hint: Any time working with compounds that have explosive properties use only non-ferrous, nothing related to steel, implements and tools.) A small bit of PP Ball and a few drops of acetone result in enough mixture to seal a small batch. A tiny drop of fingernail polish for your primer goop adds color. I wouldn't add color to any sealant for the bullet/case mouth. Experiment with ratios of acetone to PP Ball to get it as thick or as thin as you like. I think thinner is better, you want a capillary action to carry the sealant around to joint without a build-up. A piece of (very) small bore brass tube (McMaster-Carr 8859K171) works well to get a small drop to where you want it. With acetone as the solvent, drying time is minimal. The celluloid from the PP Ball makes the dried application much harder and more durable than fingernail polish alone. I've fired 20 rounds with colored sealer on the primer and non colored at the case mouth with no noticed ill effects. One round underwater for 30 minutes showed no moisture penetration after disassembling. If you try this method, I'd like to hear of your results and successes, and hopefully no failures. Thanks for reading.