From google:
Ammo Up lv 1 affects: normal 1, pierce 1, spread 1, sticky 1, and cluster 1.
Ammo Up lv2 affects: normal 2, pierce 2, spread 2, sticky 2, cluster 2, recover 1, poison 1, paralysis 1, sleep 1, and exhaust 1.
Ammo Up lv 3 affects: normal 3, pierce 3, spread 3, sticky 3, cluster 3...