The ammo isn't a bug so much, it's a server setting. I believe its been tweaked a bit for next patch, so will be better with stock server settings soon.
ge_dynamicweaponrespawn [0/1] (1)
Turns dynamic respawning of ammo and weapons on/off. On by default.
ge_dynamicweaponrespawn_scale [scale] (1.0)
Scales the default dynamic respawning algorithm by a factor.
ge_dynamicarmorrespawn [0/1] (1) [ NEW BETA 4.0 ]
Turns on dynamic respawning of armor. On by default.
ge_dynamicarmorrespawn_scale [scale] (1.0) [ NEW BETA 4.0 ]
Scales the default dynamic respawning algorithm by a factor.
ge_itemrespawntime [seconds] (10)
If dynamic respawning is disabled, this defines the fixed time interval between ammo respawns.
ge_weaponrespawntime [seconds] (10)
If dynamic respawning is disabled, this defines the fixed time interval between weapon respawns.
ge_armorrespawntime [seconds] (10) [ NEW BETA 4.0 ]
If dynamic respawning is disabled, this defines the fixed time interval between armor respawns.