Usually, the l o n g barreled firearm will fit in a vehicle or a gun safe on the diagonal.
Couple months ago, I wanted to get a gun safe, so went to TSC and looked at theirs - they had a sale at the time.
Admired a nice Cannon safe, so decided to measure the diagonal. The sales guy, a friend, was there with me as I went down to measure to the bottom left corner. Starting to get up, I fell - which I do frequently. Henry (sale guy) tried to catch me as I landed butt first on a wooden pallet. Instant fierce pain in the ---- well, buttocks!
Fast forward a couple weeks, and the VA arranged for "Community Care" - medical care close to home, instead of the VA Hospital 75 miles away. The Doc made two small holes, one on each side of the spine. MRI's had shown a fracture of the coccyx and sacrum - that Doc "robotically" put in some titanium and screws, and I woke up to no more pain in the butt!
I did find out that my longer ML's WOULD fit diagonally in the safe, and it is now here in my shop, about 15' away. And any pallets go out in the garage!