Just like the Netherlands where unmarried people cannot be buried next to each other nor can books by authors of different sex and unmarried be put next to each other. How in G-d's name will bullets coming in contact with each other cause .... whatever ....???
Where do you think .22 LR's come from?
I’m guessing they mean like the plastic thing with the holes in it for each round. But I always figured that was to keep them from getting dinged up rather than a safety issue. Although I suppose tossing the baggage around something might poke into the primer and set one off? Would be a 1 in a billion chance though - but in an airplane...
I flew to Alaska and had slugs for my shotgun in the packaging as they told me. I forgot about it on the way back and had tossed the original boxes. So I had them wrapped up in socks/clothing and in baggies. I asked first, and they said no go - I had to get rid of them.
So I unwrapped them all, dumped them loose in the baggie and walked out to the guy helping out by the taxi stand.
“Hey - ya want 9 12-gauge Bernake slugs?” - “SURE!!”
Back then it was no big deal. But given today’s ammo situation.....!
It is a known concern with tubular magazines. Tip of the bullet of one round is positioned right over the primer of the next round. Vibration from the shot may cause detonation of the round in the magazine. There is special ammo that is less likely to ignite primer of the round in front; it is discussed here.
Rimfire ammo is also somewhat a concern because there is a lot of primer compressed into the rim of the cartridge. It still takes a serious impact, enough to punch the brass in, to detonate the primer. But the same can occur if a round is struck with a hammer, or otherwise massively deformed. It won't be a serious danger outside of the barrel, but you don't want to experience that anyway. Fire is also possible.
Most new centerfire rounds are shipped in plastic or foam holders. But remanufactured rounds are shipped without them, in bulk, thrown randomly into cardboard boxes. Bulk rimfire, even new, is often poured into boxes and shipped like that. Only higher value rounds are sold in plastic.
In general, it should be pretty safe to transport rounds of all kinds just in a bag. However if they are not controlled then something hard and heavy can hit the primer. Boxes and inserts do not prevent that, but at least you know where the ammo is. If rounds are just somewhere in a bag then you cannot be sure. Either way, the chance of accidental ignition is very low.
The fear is that the hard metal cases banging against the primers will cause a detonation. Understandable. This is also the reason that bullets used in tubular magazines have blunt tips rather than the sharp points of those used in detachable magazines. Luggage handling is NOT gentle. Severe jolts are the norm.