What is the bipod rail for?

The integral bipod rail allows you to preload your bipod (press forward) to assist follow through and allow for faster second shots.  This technique really works, although you need a stiff stock to pull it off.  AR type rifles work fine with this technique, for bolt guns you need to check your rifle first.

Check your stock by pressing forward on the bipod legs with the firearm upright.  You should not detect any movement back at the barrel contact pad in front of the receiver (requires full float - this technique won't work with forearm pressure pads).

Try shooting a group at distance (800 yards or so) both ways - pressuring the bipod and floating the bipod.  Your groups should be the same, but with the pressure added, you'll be able to call your shots better as muzzle jump will be greatly reduced.