In the latest patch for Titanfall today, a new feature was introduced that allows you to adjust your framerate up to 120fps if your monitor can support it. The problem is, it seems as though the lock on time for things like the Smart Pistol are inexplicably tied to framerate as the following video clearly illustrates.

In short, the higher your framerate is set, the faster you will fully lock on to an enemy.

Fortunately, a Tweet from Respawn says that they are aware of the issue and are working on a fix for it. Until then, if you find that you're dying a lot faster to the Smart Pistol, you'll know why.