I found this online....thought it was pretty interesting.  Can anyone verify this?

It was a common practice on fighter planes to load every 5th round with a tracer round to aid in aiming. This was a mistake. Tracers had different ballistics so (at long range) if your tracers were hitting the target 80% of your rounds were missing. Worse yet tracers instantly told your enemy he was under fire and from which direction. Worst of all was the practice of loading a string of tracers at the end of the belt to tell you that you were out of ammo. This was definitely not something you wanted to tell the enemy. Units that stopped using tracers saw their success rate nearly double and their loss rate go down.

Salute,
TX-RAHMAN
BLUE3

Rahman,It depends on the ammunition but tracers often do have different ballistics. Tank gun rounds are 100% tracer for example and the ballistics are accounted for in the firing solution, so there is no negative effect there. Naturally the rounds are flying at a mile per second and due to the nature of tank combat, the enemy will normally know he is under attack whether you hit or not because other tanks in his section will be exploding from your wingman's fire.  :)For aircraft in particular, yes the ballistics are very different and they do give you away...there are numerous accounts from pilots who opened fire on german Experten only to find that they did not score the kill and have the tables rapidly turned on them. For the most part, the most common mistake pilots make is firing from too far out with a low PK, thereby giving away surprise. Only a few of the best pilots in history consistently avoided that mistake and in part it was because of the limitations of tracers and the understanding that surprise is the key to aerial victory. 9 out of 10 pilots in all wars were shot down because they did not see the attacker...the implication is on holding fire until the very last second. I have read some things about the MK108 cannon in particular where they implied that the tracer round did not have an explosive charge due to the weight of the phosphorus used as the tracer...the ballistics were different and so was the impact on the target if a hit was scored. From my experience firing a variety of Army machine guns, I can say that a machine gun is useless without them if firing into grass or trees...there is no BOT to adjust fire off of, making you completely dependant on the tracers to redirect your aim. Even tanks need them to adjust fire if you miss the target by shooting over it...ground burst is excellent to adjust aim off of, but over-line shots give you no indication of how much you missed by. As a tank gunner I was all about tracers. In the air, you can imagine what it must be like not having any idea if you are scoring hits...therefore you must simply accept them with all their limitations and get a feel for how the tracers fire vs the main rounds. When you see the tracers in the target area hopefully you know how to adjust from there. In summary, yes what you mentioned appears to be very true for air to air combat, not so much for ground combat including rifle fire, but even then in particular for infantry combat, tracers as they say, point both ways.TX-Zen"Black 6"TX Squadron CO

Tracers are also good for one thing..INDIRECTLY. You fire to the left of your target and he sees the tracers..you can bet your bottom dollar that he's going to go right, or straight up..which is EXACTLY where I want him to go for a better shot at those nice wings of his. Tracers are good for hearding your victim where you want him. You Texas boys should know about hearding !TX-SkydiverBlack 2" Impossible only means it hasn't been done YET "

Mr. CO,              I always look forward to your highly trained and educated views on all this military stuff.  Our old "White1 Moments" (now Black6 ) were some of my favorite parts of the day when we were at CT.  Keep up the great work!Skydiver:  Interesting perspective on this one.  I like the hearding idea...."Get along little doggies!!"...."Heaaaaa!"Regards,TX-RahmanBLUE3