I disagree.
I agree the effect is minor. Perhaps even very minor. To me and others this is a game of very slim margins indeed sometimes. If encountering pilots of equal skill, planes etc. etc. etc. Subtle things in an encounter can be just the thing that makes the difference. Yes I know how to bleed fuel and the like.
I respect that your opinion may be different than mine. Again, I agree the effect is minor.
Factually, it is a pure data point. It does exist in the context of pure facts.
There is no "slim" margin. If you and I up a 110, Mossi, etc, and you dump all your "worthless" .30 cal ammo be it in the rear defensive guns or front guns, I still can do everything you can do regardless if you're 100 lbs lighter or not. Each and every move you do I can match and in many cases out perform you because I know the edges of stalls better, how to use the rudder better, how to use the torque to my advantage better, etc, etc. Stop telling yourself that dumping ammo "helps" you and you'll be a better virtual pilot. Trust me. You'll be far better off listening to others when we say to "learn the plane", burn off the fuel, etc, than to do gamey things such as dumping your ammo. It does not work. Seriously.