It's called a "two-stage pull". Universally found on milsurps since day one. The idea was/is to give the sear a really deep bite to keep the striker from accidentally jarring off under extreme service use. The first half of the pull, which is very light in nature usually, is on a cam which draws the seer engagement apart almost to the point of letting go- taking most of the deep bite out of the "at rest" engagement. At that point then, the seer lever comes down off the cam and the pull gets a little harder to overcome for the last little bit of engagement.
Unless you completely understand the subtle geometry of one of these triggers, it's a really smart idea to let them the heck alone. It's easy to muck it up and end up with an unsafe trigger. Best advice is that if the second stage pull is nasty, some judicial stoning/polishing can be done to the seer and cam surfaces to smoothen/lighten the triggers somewhat. Rather than doctor the trigger into a single stage pull, my advice is to simply replace it with a Timney or something.
Shoot it a while and get used to it. You'll be surprised how efficient it is, and how second nature the management of it becomes after getting accustomed to it. After all, a bazillion soldiers learned to use them- you can too!