The stock, or buttstock, describes the part of a rifle that receives the barrel and firing mechanism and allows the weapon to be held comfortably against the shoulder. During World War I, rifle stocks had the same basic look and feel: a solid butt, a fore-end situated beneath the barrel and a grip, all fashioned from wood. The grip could be quite subtle, consisting of little more than a slight notch or pommel located just behind the trigger.
This was the way of the rifle world until 1942, when Germany introduced the Fallschirmjäger Gewehr 42, or FG 42, a weapon designed exclusively for parachute troops. The FG 42 possessed a few unique features, including a side-mounted magazine and a bipod. But one of its truly revolutionary enhancements was a sharply raked grip that extended below an in-line stock design. This marked the beginning of the pistol grip, and it gave the shooter certain ergonomic advantages, making the weapon easier to aim and improving accuracy.
The pistol grip remains a defining characteristic of assault rifles and, by extension, of assault weapons. In the ban proposed by Sen. Feinstein, any semi-automatic rifle that can accept a detachable magazine and has a pistol grip would qualify as an assault weapon. The legislation also targets thumb-hole grips, a popular workaround under the 1994 ban. A thumb-hole grip -- a stock with a hole bored through the butt just behind the trigger -- functions just like a pistol grip, delivering the same beneficial ergonomics.