+Totally believable! And in support I refer you to the current issue of "Guns" magazine May, 2013, page 24 to a story by Clint Smith that details three incidences of ammo detonation outside of the gun. One was some .45 ACP held in moon clips that he was tossing into a bucket of ammo, one fired, blowing a hole in the side of the bucket.

Another incident during a class occurred when a student tossed a loaded .45 magazine behind the line and a round fired. And lastly, he mentioned a box of lower .25 ACP that fell from the counter in a shop and a round was fired.

So, yes, it does happen, very rarely thankfully, just a reminder to take care!

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Old paratrooper in NC