Take the plastic top off any spray bottle and put it on the floor of the safe then put your muzzle in that. A small piece of foam can be cut to fit in the cap.

"word of caution"

If you store muzzle down, be sure you do not have a conductive or corrosive surface under that barrel. Metal, concrete, vinyl with moisture, and even carpeting with moisture can result in corrosion of the steel. Sometimes plain rust, sometimes galvanic corrosion. Best to put down a nice piece of dry pine, even if you use a sleeve. If you store in a thick padded case of some sort, that will eliminate this problem.

I once saw a nice Kimber .22 with a muzzle that looked like a rat had chewed on it. Owner admitted it was stored barrel down for 18 months in his basement (in a cotton sleeve). I cut 3/4 inch and recrowned. It shoots better than ever, and he still wonders how I "fixed" that barrel.

Roger

A 3" thick piece of upolstery foam between the pad and the floor or bottom of the safe will also cure the problem.