Taboo, you could have also used the knife tool for cutting. You select the edges you want to cut then press shift+k or whatever it is in the new Blender. Then you click, drag a straight line and click once more to set up the line you want to cut. Once done, press numpad enter. If you press control, the line gets snapped to the nearest vertex.
lol looks like you're using an airsoft cleaning rod as a bipod
cool dsr
so that's what it is