Does it use ammo when he fails to achieve a valid shot with the d10 roll ?
Undecided - Maybe your group can take a survey and discuss it.
My impression is that they were fired, with a higher percentage of tracer more to dissuade or discomfort attackers from the rear rather than with the idea they could actually be aimed with any effectiveness.
My un-researched feeling is that either the pilot or the rear gunner would trigger them whenever they saw someone or became aware of someone lining up on their six. Since pilot controlled stinger guns relied on noticing an attacker in a mirror or periscope. I don't think deliberate aiming was really expected.
Therefore - I think it may be logical to expend a normal shot any time you roll the D10 to see if you even get to resolve a shot. The plane is firing at the attacker, with a chance that the attacker may blunder into the fire.
JD
(https://groups.yahoo.com/neo/groups/FW_Referee_Central/conversations/messages/2593) 17/05/2014