anything as long as the bore fits :D put one in, and blow it out - it should pop out with a little force but not too much - thats good.
Havnt had a single one bust out of many cases. Cant see them zipping through the air easily - they are black-skin, so its harder to dodge them (you know what i mean, you cant see them coming), yet the fill is bright pink (or whatever you get). cheap.
Nothing, unless they are being shot at you.. Keep them in an Igloo(TM) so theyll stay nice and warm and the moisture will stay out, they should store OK.
Very cheap - 45$/2000, like-Marb performance - dont curve, break every time, etc etc. I dont know if they do mail-order but i live near Cobra and these thinkgs are the awesome. Get some if you live around San Diego area.