I came across these downloadable fact sheets from Northrop Grumman today. Click through the different categories to find them.
The fact sheets are all 1-page documents, so brief, but still interesting. Some nice cross-sections are shown on the medium and large caliber sheets. NG produces small, medium and large caliber ammo, so something for (nearly) everybody!
There is also this 28-page small caliber catalog:
And the same for the Bushmaster Chain Guns they make: