1. Go to the Virtual Arsenal.
2. Select any Mk1 EMR weapon.
3. Reload weapon first and continue tapping your reload key constantly and fast.
4. Noticed that the reload sound doesn't play on the second reload and so on. If you were to constantly tapping the reload key.
Something like this, first reload will play a reload sound and the second will not. Than the third will play a reload sound and again the fourth won't. This goes on and on.