My dealer has American Eagle safes made by Cannon, with full Cannon warrantee, for under $800, on a special promotion.
Don't know if it will hold twenty long guns, but I think it might hold even more than that, with the right interior set up.
Mine is set up for mostly handguns, but one shelf is cut out for long guns on both sides, if you don't use the sliding cover over half that shelf.
Also has the brass combo lock with three spoke handle that I prefer, though the electronic lock is available, but I think at extra cost?
I've yet to find a safe this nice, as inexpensive.
Bill