I like the 223 round and have used it since the early 70's when all that was offered was the 55 grain rounds . I have a few thousand rounds of brass for it . The brass by it's self won't do any good with out the other components it takes to make it a viable round . You can put several thousand rounds in an air tight military surplus 50 cal. ammo can . Kept dry and in an even temp. area , military surplus 5.56 ammo is made to be stored for periods of time as was the 7.62 nato round . They may not be your first choice for a hunting round but shot placement is a big factor with them . they have a sealant around the primer and bullet that helps keep them from absorbing moisture as well as off gassing from the powder so it doesn't break down as fast . As with your food stuff you want to rotate through your ammo supply so I find that marking it with a date helps there use the older lot first and replace it as you use it . So then in times of short supply you will have some and you don't really need to hoard a ton of it unless you are just going out and blowing through hundreds of rounds in a day . In that case you aren't going to survive long any way if the S h t f .