KT has a friend who is a survivalist and he has several rifles hidden in different places on his property and on some mining claims he holds in the National Forest here in Arkansas.
I have seen his preservation methods and they could be found but not easily, but have little doubt the rifles would be in good condition.
You take 4 inch schedule 40 PVC, cap one end, cut off to about 18 inches longer than the rifle, lube rifle heavily, then wrap in cheese cloth, insert in tube, then insert several bundles of ammo similarly wrapped in cheese cloth, and finish off with industrial size cloth bag of fresh dehumidifying chemical. Seal with glued on cap on open end, do this on a low humidity day.
Each rifle is buried this way, all laying next to each other. A small amount of dry dirt or aggregate is placed on top of the tubes to cover them, then concrete wire, 6 X 6 mesh is laid in foundation, but cut in place. When the concrete is poured, all the wire but this one place is set up on bricks, this wire is set up on its on set of bricks. This way not easily found with MD, but owner marks a nick or sign on the concrete, indicating to him that his is where you break it. Easy to recover with an 8 pound sledge. In less than 2 hours you can have them all out and be on your way!
He has also buried them around in the woods on his mining claims similarly packaged, but has scattered railroad spikes all around the adjacent area to keep MDers busy diggin them! LOL
KT told him He would rather have his Royal Rifles loaded and handy at the Castle should the Big Sh*t start up!
Concerning the comments about concrete cracking mentioned just above, KT has no doubts about freeze thaw problems but down here in the South, nearly all concrete slabs have 6 inch steel concrete wire mesh in them, including our highways. We have little problems with that effect on exposed concrete.