From Data Realms Wiki
Tracers are special bullets that ignite upon firing, making the projectile visible to the naked eye.
Below is an example of a tracer round, note that it is exactly the same as a normal round so an explanation is not provided. Usually the only difference is the color, but the two rounds don't even have to be the same class of object. Tracer rounds are optional.
A standard bullet tracer is set up something like this. For an explanation, see round.
AddAmmo = Round InstanceName = Round Gun Tracer ParticleCount = 1 Particle = MOPixel InstanceName = Particle Gun Tracer RestThreshold = 500 LifeTime = 1500 HitsMOs = 1 GetsHitByMOs = 0 Color = Color R = 247 G = 247 B = 147 Atom = Atom Material = Material CopyOf = Bullet Metal TrailColor = Color R = 255 G = 255 B = 159 TrailLength = 45
The Round To Tracer ratio is found in the magazine;
RoundCount = 11 RTTRatio = 4 RegularRound = Round CopyOf = Round Gun TracerRound = Round CopyOf = Round Gun Tracer
Above shows that there are 11 rounds in a magazine, and every fourth round is a tracer round.
Below is an example of a magazine with no tracer rounds;
RoundCount = 11 RTTRatio = 0 RegularRound = Round CopyOf = Round Gun
TracerRound is simply left out, and RTTRatio is 0; either one of those would result in no tracers.