I have problems finding 10mm ammo for 10mm gun and 5.56mm for assault rifle, Moira don't sell them anymore, anyone know where I can buy some? I mostly seem to find ammo I don't use as much. Thanks.

Flak 'N Shrapnel's in Rivet City

Chief Gustavo in Tenpenny tower

Outcasts are useful for ammo too if you go to their base and cut a deal with them.

Tulip at Underworld, Karl at The Family, Michael Masters if he's in Tenpenny, Knight Captain Durga at The Citadel. Seagrave Holmes at Rivet City may sometimes carry a few rounds. If you're really low on ammo, make a shopping trip, wait three days for a respawn and make the rounds of the vendors again.

Cool thanks, where is the Outcast base btw?

Ft. Independence. It's southwest from Megaton about halfway to Tenpenny Tower. If you follow the road that goes up by Vault 101, it will take you right to it. It's the large building on the right and it's a little lower than the road.