[quote=Dinh AaronMk]
Use itself wouldn't be the only factor in how many rounds are left around either. You got to take into consideration the environment their in. I wouldn't doubt that over time the powder or the casing of the bullets would deteriorate over time leading to a situation where they could misfire or are inoperable. You can only make matters worse by storing them inappropriately. Moisture can deteriorate the casing or even the lubrication between it and the bullet itself. [/quote]

Its kind of hard to store rounds improperly unless your outright do so like in the mud, dirt, and just left there. There are many stockpiles of 50-60 year old ammunition still being sold off, commonly known calibers like .303 and 7.62x54mmR. Going to sites like gunbroker will yield ammunition that can be easily 100+ years old. Another thing is that Fallout doesn't like to put expiration dates on some of their things, as is known with the number of microwave entrees that you can go out and find.

While moisture is a valid issue, the post-nuclear wasteland in most places doesn't have to deal with it. In fact the dry heat that would be common in most places is excellent in preserving things, proof of this can be seen in the Dead Sea Scrolls.

[quote=Dinh AaronMk]You may also get a lot of people who aren't trained to use guns as the US Military is. Even consideration to "Spray and pray" tactics are given then the number of rounds that would hit a target raises even higher than they do already.[/quote]

This is a true fact that I kind of skipped over, however, it wouldn't effect much as there are still tens of billions of rounds. Plus it doesn't take long for someone to sit down and try to study a weapon system to learn it. You could easily devote a good 4 hours of each day of a weekend to learning the basic operation, loading and firing of an AR-15.

[quote=Dinh AaronMk]This is on top of military stockpiles no doubt being in places that would have been nuked in the exchange and damaging them further, trapping them under heavy rubble, or just making the conditions in retrieving them all around unfriendly to the lay scavenger.
[/quote]

This is a very valid point as well, however a number of places in all the games have former military installations that weren't attacked, DC is filled with them. The White Legs were able to obtain a large number of rifles, machine guns and ammunition from a National Guard armory and it was enough to arm the few hundred or so that made up the White Legs.

All valid points either way.