[GonzoGOP]

In Call of Duty 2 ammo has no mass. Unfortunately in real life ammo gets heavy fast. If you are planning on forting up, this isn't as big of a problem. But if you are planning to ship out, then there is no reason to have more ammo than you can bring with you. If you intend to lug it around with you figure out how much you can carry / load in the car.

The obvious exception, as pointed out by another poster, is practice ammo. You can burn up a lot gaining and maintaining proficiency. And don't forget to rotate your stock. Ammo has a use by date, and if you want to avoid a misfire at a critical moment, use up the old stuff as you buy new ammo.

[DuncanWaring]

Ammo has a use by date, ...

Not that I've really noticed.

I've used ammo over a half-century old that has worked as well as new-manufacture.

1960's-era "Pakistani Ordnance Factory" (POF) .303 Brit being the notable exception.