I live in barn conversion and although I have brick work walls downstairs the bedroom upstairs are timber stud and just plasterboard over
if you find the studs cut out the plasterboard fit additional stud in line with bolt holes for gun vault using existing stud for the other holes , I then used 100mm timber locks (caution on size of stud on this ) use over sized washers to really clamp the vault to wall , a good impact driver drill and it’s as good as to masonry if not better imo ,I wouldn’t fix to the floor unless you know exactly where your pipes run