FWIW, rifle stored with their bolts open/back can be stored close together
That's what I do, as well.
With standard bent bolts, the open bolt tucks in behind the stock of the rifle next to it. With a little twist of the rifle, you can slide it right out (without hitting anything).
If none of us cared about our rifles, we wouldn't have to worry about things like this.
...Just toss them in the safe and slam the door shut, before they fall out.