You can use an endcap on one end. Teflon tape on threads, but if buried, assume that even if it doesn’t leak that you will have condensation and package things for a damp environment.
Your right.
I’m one of these folks that just look at burying anything is just counter productive anyhow.
If things were ever to the point that we are burying stuff, it’s time to NOT bury stuff cause your gonna need the stuff to protect your stuff.
I buried one using that very method, but I filled the tube with nitrogen before sealing. When I moved 5 years later, dug it up and just as good as new.
1. Seal one end PVC pipe, sealant glue on cap.
2. Grease or heavy oil weapon, clips.
3. Seal shells in vacuum pack bag.
4. Insert all contents into pipe.
5. Heat pipe interior and contents with hair dryer
6. While warm & dry, glue on other cap.
7. Bury below frost line.
Try to remember location.
American TSA, FEMA and together with other FED resources will gladly assist in kicking down your doors and providing brown shirt services as American traitorous JANISSARIES.