FMJ = copper or brass alloy, non sparking.
Aluminum DT again, Non sparking,
You can take a file, or other piece of hard steel, hit it on the right rock and get sparks all day long.
Hit copper, brass, or alloys containing these, or aluminum alloys, and never get a spark, EVER.
FMJ does not mean its cast in steel or iron. Means it has a full metal jacket of brass/copper allow wrapped around the lead core.
And no a tracer round won't ignite the fuel "in the tank" by passing through it.
It might possibly ignite VAPORS, but not the fuel.