In short: No, No ammo is wasted from reloading a non-empty clip.
Now Killing Floor's system is sort of different from that of other FPS games, in the fact that it shows you, in the bottom corner of the screen, the amount of ammo in your current clip, and the amount of clips you are currently holding.
For example my medic gun (at lvl 5 medic) has a clip size of 64, and can hold 6 clips of ammo:
This means that I have
64 + 64*6, or 448 bullets to fire at some mutants.
When I fire ten shots, and then reload, my magazine gets restored to 64, and my clip size will not change. Now wait before you say "Clip size doesnt change? awesome that means I have infinte ammo! :D", because you have spent those ten bullets, the number of extra clips you have left has simply been rounded. So after firing ten shots, you now have 438 bullets left, which is 64 in your gun, and 374 / 64 in your spare clips, which is about 5.84. Now rather than say "Herr Derr you got 5.84 clips left!" the game makes it easier on you by rounding the 5.84 and letting you know that you have approximately 6 clips left.
The fact that this number stays at 6 proves that you do not loose the extra ammo in a clip while reloading, due to the fact that if you did, you would lose 64 shots each clip every time, so after shooting only a few and reloading, the extra clips count would be 5:
448 - 10 bullets shot - 54 remaining in clip - 64 put into new clip = 320, 320/ 64 = 5
Where as killing floor does it this way:
448 - 10 bullets shot - 64 put into new clip = 374, 374/ 64 = 5.84 ~= 6
- Fully Loaded Gun
- Shoot a good number of shots
- Have fewer ammo clips
Now this time we'll only shoot a couple shots:
- Shoot a couple shots
- Have the same amount of ammo clips
Therefore there is no ammo lost upon reloading a partially empty clip.