Question: What is the typical shelf life for ammunition?
If ammo is stored in cool dry place, preferrably in an army .50 cal. ammo can, it will last a life time with no trouble. I was recently shooting some 7.65 Mauser ammo made in the early 1930’s in Belgium and it is still sure fire.
Old ammo that has been kept clean and dry should be good longer than you'll live. More recently, there have been changes in primer formulations to reduce lead. The old lead styphnate primers have a very long life if kept clean and free of oil. Newer formulation (DDNP) is susceptible to degradation by moisture. Shelf life of commercial "lead free" ammunition is about 5 years according to Fiocchi (an ammo manufacturer).
There has also been a move to go "lead free" with the ammunition. A tin/tungsten formulation has been touted. The problem is the tungsten make the bullet very abrasive and results in rapidly worn out barrels. Most barrels will last 20,000 rounds with good lead or copper/lead bullets.
That is a very good question.
For centerfire ammo - Prior to Al GOre and “Green” primers, I would say, 100 years (proper storage and all that) - I have fired ammo made in 1947, Russian even, and it all went bang... split and seperatd case not withstanding.
Now, with the “Green” primers I would worry after as little as 10 years.
All the ammo I have purchased of late is furrin made/surplus with the old time type primers. In sealed can, in pritine shape - after ammo from open ammo cans were examined from the same lot.
.22 ammo will normally work if it is clean and stored properly.
Keep it dry and below 80-85F, a long time, WW2 ‘06 ammo still goes bang and will reach out and touch...anything you aim at.