A “bullpup gun means the magazine is fed into the gun behind the trigger rather than in front. The main effect of the bullpup design is that rifles can be shorter without losing any effectiveness. The gun can install either a three-round grenade launcher or a shotgun. Shotguns are useful in close quarters, while grenade launchers give more range than just hand-tossing a small explosive. The main gun fires 5.56 ammo, a standard NATO round.
A video with three other bullpup guns
Steyr AUG vs. FN 2000 vs. IWI TAVOR
IWI Tavor was favored by the reviewer. He explains how the bullpup design allows for a more compact rifle while still leaving a longer barrel.
The Steyr AUG (selected in 1977) is often cited as the first successful bullpup, finding service with the armed forces of over twenty countries, and becoming the primary rifle of Austria and Australia. It was highly advanced for the 1970s, combining in the same weapon the bullpup configuration, a polymer housing, dual vertical grips, an optical sight as standard, and a modular design. Highly reliable, light, and accurate, the Steyr AUG showed clearly the potential of the bullpup layout.
The IWI Tavor is the Israeli Battle Rifle.
The Singaporean SAR 21 addressed one flaw of bullpup rifles by using a stiff sliding plate to improve the quality of trigger pull, and by using a shell deflector to achieve a slightly ambidextrous weapon.