That would be because First Curse high ludicrously high base range, and then built in range finder, and a precision kill gives you rangefinder again for the rest of your now refilled magazine, and the naturally slower rate of fire forces the guns bloom down smaller before you can even fire again compared to faster HC's. The issue is with High HC's, is that they have a lower time to kill then their medium counterparts. They can two tap people with low armor, whom very few people do and it is outright impossible to two tap a Titan. It otherwise is the exact same shots to kill as the medium HC's. You can find success with it and other HC's in the same class (like Timur's Lash) simply on the notion that it's more reliable, but it's reliability comes at the cost of kill time.