Unfortunately there has been no official confirmation of ‘how long’ is shortly after reloading.
From a few tests that we have done and speaking to other members of the community the time is around 5 to 7 seconds.
We would advice to try get kills under the first five seconds after reloading just to be sure.
What’s the best way to complete the challenge?
The best way we’ve found that works a treat is to go on the Shoot House 24/7 map, you’ll start racking up kills and need to reload often.
We found that we didn’t even have to concentrate on trying to do it with the map being so small you pretty much always get a few kills a game.
If you’re really trying to get it done the best way to do it. Is to shoot a couple bullets whilst stood around a corner. Turn your volume up so you can really hear footsteps and have sleight of hand perk on your weapon. So as soon as you start to hear someone coming quickly reload and surprise them whilst jumping out.
Another Great Tip
Once you’ve killed someone don’t reload immediately. Wait until you hear someone coming and then reload. (Make sure your gun is reloaded before they come round the corner though)
Timing is pretty key on that one though.