I bought a wee ex army ammo tin and got a boy to weld a bit on it for a padlock. I do know lads who just used cash boxes. Now, indeed, that was in the days of all the ammo going in our hold bags - which mine did in October with Emirates going to Zim. I doubt if I've fired 20 rounds on any trip to Africa - even on the culls. They were 13 animals each right enough and I added three trophies on top. 16 plus 2 at the target. Hmmm. A bit tight. I must have had two rifles then. So old I forget!
The questions is, at what point do they tell you that it needs to be checked separately? Bloody pointless if you get to check in - even exceptionally early as I'm sure all the shooters do - and they say no to going in bag. Then you are well stuffed.