SMG bullets could kill at 300 yards, but accuracy wise, most SMGs in WW2 were around 50-100 yards accurate, and that was with highly controlled bursts or single shots. Only the Suomi and Ppsh were more accurate.
Also, tracer rounds really were not used in machine guns when shooting at land targets for the obvious fact that they give away your position for no real gain, since the shooter can't actually see the tracers anyways. Tracers were used in AA machine guns so observers could watch the fall of the shot and calculate the lead needed, but that simply wasn't a thing for short range ground combat. Instead, tracers would easily show the enemy exactly where to shoot to silence the MG.