In the U.S. there is nothing specific needed in most states, but you have to 18 to purchase shotgun and rifle ammo, and 21 to purchase handgun ammo, so you might be asked for ID. Illinois, and I think a couple of other states, require residents to have an ID card to purchase ammo.
18
Ask at your local gun shop where you purchase your ammo.
Yes.
Ammo in .25 rimfire has not been available for many decades.so the answer is no.
yes
Anyone 18 or older can purchase a firearm in Texas (from a private seller). Only licensed dealers can not sell a handgun or handgun ammo to someone under 21.
There has been an all time high in the purchase of ammo. When things are scarce, the prie goes up.
It is not possible to purchase ammo further than the 5 you receive each time you visit your crib.
Some places to purchase ammunition for a 9mm gun can be found at some of the following websites : Lucky Gunner, Ammo Man, Cheaper Than Dirt, and Bulk Ammo.
If you reload your own ammo you can purchase brass from Midway USA. if not you can order loaded ammo from http://www.qual-cart.com/2536mar.htm
Once can purchase an ammo box at a military supply or army navy store, online through Amazon or eBay, or from an individual by answering a classified ad from Craigslist or local newspaper.