How about a little pixel shading or bloom effect to apply to the tracer rounds, so they look a bit more "glowy" than just "white"?
Not so fancy and glowy like IL2/FB tracers, which you can see out for miles, but still a little glowy feeling would help the trigger happy folks a lot more satisfied when they let 'er rip.
Would this be too much of a resource hog? I hope not..