Best places I’ve heard to bury guns is in a junkyard or some place where lots of nails have been strewn. I know of several old houses that burned decades ago which might be a great place to bury them.
Or you can buy a keg of nails and “salt” an area to confuse a metal detector.
Suspend them down in an effluent holding tank.
I’ve heard the same thing. Sounds like an ordeal to carry out but might be worth it in the end.