Another interesting effect I have big problems with is that you can't fire a burst of two or three shots and still be able to hit your target with two bullets.
In fact, assuming I read the rules right, you must spend a minimum of six shots to be able to hit anything with two bullets!
This is why I think the number of bullets used and the number of hits achieved should not correlate on the ammo dice. I think this could be solved by altering the way the faces are numbered, but a simple solution would be to roll the ammo dice once to see what hits you get, and then roll them a second time just to calculate how many bullets you used.
Overall though, I would much prefer a design where ammo capacity was given in bursts, and 1 burst = 1 ammo dice, and the ammo dice were just marked with hits or mishaps, not numbers. You don't count individual bullets, just the number of bursts you have. For semi-automatic, we'd assume you're firing multiple shots. For single shot weapons like sniper rifles and bows, you don't use ammo dice and just count individual shots.