The gendarmes decreed that we had to upgrade our firearm storage though they had (as far as we could tell) safely and happily lived in the same cabinet for over thirty years! We had to buy a safe. Fortunately gun safes have become much less expensive over the years. We carefully chose one from eBay for $300 http://www.ebay.com.au/itm/271310053701?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT which would fit neatly in the space where the old one came out. This one claimed to be an 11 gun safe though I would say you could squeeze a few more in without much trouble.
The metal walls are a bit thicker than the old modified locker, and the locking mechanism is much more secure. However, I think I could get in through the exposed side of it with an angle grinder in a little while without much trouble. This got me thinking:
I noticed you could slip a sheet of aluminium checker plate inside the safe – attached loosely up against the exposed side. There is a narrow space behind the door hinge which would hold it on one side, and you could hold it in place with a couple of screws into the wall at the back. It is important it is loose. Then when someone cut through the steel plate their angle grinder disc would instantly stall against the wobbly aluminium (have you ever tried to cut that stuff with an angle grinder?) and shatter all over the place – hopefully taking one or two of the potential burglar’s eyes/fingers with it!