Safes that weigh 1000 lbs (empty) and up are tough to move if you don't know how and have a good pallet jack or something similar.
But they're quite easy to tip over.
And once they're tipped over, they're mostly all VERY easily pried open with pry bars and crow bars. Or they can be cut / bashed into.
REAL bona-fide safes big enough to put long guns in will START at $6k. And they go WAY way way up from there.