2 | land must have mil>0, glim>0, gun>0, shell>0, eff>=40, and not on carrier
20 | at sector that doesn't exist
22 | at ship that doesn't exist
26 | at valid target, but no mil
50 || land firing nowhere (shells consumed)
54 | at ship out of range
56 | at sub, server pretends out of range
61 || land firing at bogus target
68 || land firing at undefended target
69 | 100% hat with one gun
74 | likewise one shell (take care to avoid automatic supply)
85 | at sector, fractional range, ~50% chance