Actually,we have have some sort of limit for total mass of ammo in checked baggage in the US on airplanes as well. The difference being nobody here is flying around looking for ammo deals. I know there are rare instances where people ship ammo to their hotel or to destination contacts if they travel to subgun matches or MG shoots, although most people would be willing to drive a day or two if they were bringing that much gear for fear of theft. Keep in mind you can mail several thousand rounds of rifle ammo in the US for maybe $30. I buy cases (1000 rounds) online when there are free shipping offers. I know you guys pay way more to ship ammo.
I've only carried half a case of ammo at most on airplanes for self defense and maybe a quick range trip at my destination. Places to buy ammo are not exactly rare in the US, so I can get regular amounts of ammo when I get where I am going.
I've also been lucky in that all the states I have flown to in recent years allow me to carry in the airport. So I am armed when check my guns with the counter, and I rearm at my destination in the bathroom before I leave the airport. TWO TIMES I had baggage counter women ask me a weird question when I said I needed to check a firearm.
"OK, do you want to check it in you checked baggage or do you want to carry it onto the plane?"
WTF?
What I wanted to say was, "Well, what are my options?
"
What I did was look around, and then say, "I think I'm going to check it in my baggage"
No idea where that comes from. I guess they are thinking of air marshals or pilots.