I had a .22 hangfire in my Buckmark about 6 years ago. Obviously factory ammo, and it took almost 90 seconds for it to go off. I was showing the GF the right way to wait (pistol pointed safe direction etc), for a minute, but took longer as I was explaining it to her. When I went to extract the round, it went off just as the slide opened. Not from the ejector hitting it or anything. The round, and other fired rounds, were sent back to Federal, along with the rest of the lot of ammo, and it was found to be defective. I got $200 or something plus 10,000 rounds of free ammo from them for that.
So .22's aren't any safer.