most RSC's have interiors that are sized for bb guns..
so by the time you try to put scoped rifles or double barrel shotguns in
you'll be trying to modify the interior..
you can make your own racks and put them in, or use some pre made ones and modify them..
you can also look for something called rifle rods
these are a non metal rod that goes down the bore, the top of the rod has a large button on it and attaches to the interior of the RSC by velcro to hold in place..
note:RSC=residential security container
here are some ideas
http://www.deansafe.com/rifle-rods-10-pack.html
you can also search through past threads in the accessory section to see what others have done.
http://thefiringline.com/forums/showthread.php?t=488783
there are some members here that are security dealers that maybe able to help as well..
best of luck..