I found this on a forum. It would make a great barter item in the stereotypical post apocalyptic world that survivalists are always crapping on about.
The forum post is as follows:
The "any gun" ammo pouch is intended to allow you to load the most random types of guns. It can be cached or could be traded as a barter item post SHTF. Originally created by Boston T Party and published in his book Boston on Surviving Y2K.
In a small belt pouch, pack 5 rounds of the following:
.22 Long Rifle, .25 ACP, .32 ACP, .380 ACP, 9mm, .38 Special (which can be used in .357 Magnums), .40 Smith and Wesson, .44 Special (which can be used in .44 Magnums), and .45 ACP
Pack the rounds in waterproofed packages such as zip lock bags.You will also need shotgun shells.
Pack 2 round packs of the following: .410, 20 gauge, and 12 gauge.
Finish the ammo pack with 5 round packs of the following rifle ammunition:
.223, .243, .270, .30 Carbine, 7.62x39mm, .30-30, .308, and .30-06
This ammo pack will probably 90% of all the firearms in America.You could add additional rounds, such as 9x18 Makarov, .357 Magnum, .41 Magnum, .44 Magnum, 7mm Remington Magnum, .30-40 Krag, .303 British, 8x57, .300 Winchester Magnum, and other fairly common calibers. This would result in an exhaustive ammo pouch, but it would sacrifice some portability in doing so. Remember - ammunition is heavy.