With creative "leaning" (guns at an angle along the side/back walls), besides removing all the shelving except for a full-width shelf 6" from the top/roof, I easily fit 30 rifles into my "22-gun" Cannon safe, including their scopes & bolts (the BA rifles have their bolts open/back) - and none touch each other (barely).
NO slings allowed, though.............
My Cannon's interior, however, has an open front to the two sets of rifle racks/rests, and not the closed front/bar that many safes have, that require tilting the rifle to get it out - IMO setting up an easy hit on it's neighbor.
One half of the top shelf's for important family papers; the other half's for handguns (8 at present).
The bottom of the safe, betwixt the rifle butts, has room for a Golden Rod dehumidifier on one side & a loose scope or three on the other.