A word of caution.

The 5X ammo does pitifully little damage compared to the 7x ammo (the stuff that costs
real money). To add insult to injury, if you actually use them in game, they are so
expensive credit wise per salvo that you will finish the battle LOSING credits. I tried
them a while back and regardless of how well I did with them I wound up losing credits
every time.

kk

ya wht he said and basically you have to buy the shells. $2 for every 80 shells.

The 7x mortars require premium ammo that you can buy with the store... or sometimes win in
events (like the current everyday party event).
The advantage is, that the premium mortar has more damage, faster reload and the ammo only
requires 0.1 weapon space... so you can load loads of ammo onto almost any ship...
The 5x mortar has normal ammo that you can purchase with ingame credits, but has less
damage, longer reload and requires normal shell space... and the ammo is rather expensive
(500 creds/shot) so using when low level is almost impossible...