It took a little digging since I have the AvHistory Effects files always as part of my installs.
If you have only the plain vanilla effects then the weapon files will need to be edited for the stock tracers to show up.
In the Weapons folder:
37mmNudelman_round becomes
<?xml version="1.0"?>
<UnitData>
<General Allegience="" LongName="" ShortName="" ModelName="" BlastDamageScale="1.0" ImpactDamageScale="1.0" FireDamageScale="1.0" Priority="2" Type="weapon" EnteredService="01/01/1943" BlastDamageMod="0" ImpactDamageMod="0" FireDamageMod="0" AllowSpawn="n" Category="weapon" Country="Germany" Mass="0.685"/>
<Description String=""/>
<Weapon WeaponType="shell" ImpactDice="1" ImpactDieSize="1" ImpactOffset="650" BlastDice="1" BlastDieSize="1" BlastOffset="3300" BlastRadius="3" FireDice="1" FireDieSize="1" FireOffset="71" ExplodeEffect="fx_grndexpl_t" GroundEffect="fx_grndexpl_t" AirEffect="fx_airexpl_s" WaterEffect="fx_bltwtr_l" TracerEffect="fx_tracer_m"/>
<Loadouts/>
<GunStations/>
<DamageBoxes/>
<Systems/>
</UnitData>
23mmNudelman-Rikhter_round becomes
<?xml version="1.0"?>
<UnitData>
<General Allegience="" LongName="" ShortName="" ModelName="" BlastDamageScale="1.0" ImpactDamageScale="1.0" FireDamageScale="1.0" Priority="2" Type="weapon" EnteredService="01/01/1944" BlastDamageMod="0" ImpactDamageMod="0" FireDamageMod="0" AllowSpawn="n" Category="weapon" Country="neutral" Mass=".531"/>
<Description String=""/>
<Weapon WeaponType="bullet" ImpactDice="1" ImpactDieSize="1" ImpactOffset="65.39" BlastDice="1" BlastDieSize="1" BlastOffset="52.8" BlastRadius="2" FireDice="1" FireDieSize="1" FireOffset="25" ExplodeEffect="fx_grndexpl_t" GroundEffect="fx_bltgnd_m" AirEffect="fx_bltpln_m" WaterEffect="fx_bltwtr_m" TracerEffect="fx_tracer_m"/>
<Loadouts/>
<GunStations/>
<DamageBoxes/>
<Systems/>
</UnitData>
The lines that are missing from the Effects.xml to support the intended green tracers are:
<tracer_23mm_green ClassName="TracerEffect" TracerLength="2.5" TracerWidth="2.5" TracerRorationSpeed="500" TracerBlendMode="Add" TracerSideTexture="tracerend7.dds" TracerEndTexture="tracerend7.dds" SmokeLength="1600" SmokeWidth="2.5" SmokeRorationSpeed="1200" SmokeBlendMode="QuadSprite" SmokeSideTexture="tracerSmoke4.dds" SmokeEndTexture="black.DDS"/>
<fx_tracer_23mm_green ClassName="GroupEffect" Effect0="tracer_23mm_green" />
and then you would need to add tracerend7.dds to your Effects\Fxtextures folder.
black.dds and tracersmoke4.dds should already be part of the basic install.
View attachment Tracerend7.zip