The T-40 is a grenade launcher of Turkish origin. The T-40 was developed in the 1990's for use on the G3 battle rifle that is in widespread service in the Turkish military. The design is a mix of two proven designs: the US M203 and German HK 79. Most of the design is based on the M203, but the redesigned trigger mechanism and mounting bracket are based on the HK 79. The result is a better weapon than the M203 at a lower cost than the HK 79.

The T-40 is mostly a copy of the M203 and looks rather similar. The T-40 is a breech loaded grenade launcher that uses standard NATO low velocity 40mm grenades. In order to load a grenade the barrel is moved forward and the grenade is inserted. The weapon is cocked and ready to fire when the barrel slides back in position. The only parts that differ from the M203 are the mounting bracket, barrel release and firing mechanism. The T-40 has a thumb operated trigger on the left side. This position allows for a better balance in the firing position and reduces the time to reach the trigger since the hand does not need to be moved. The barrel release is located in the same position on the right side.

The T-40 is a single shot weapon that fires 40x46mm low velocity grenades. Besides the standard high explosive fragmentation rounds there is a wide selection of other rounds available. Due to the distance that the barrel slides forward upon reloading not all types of grenades can be loaded due to their length. An experienced operator can fire 5 to 7 rounds per minute. The effective range against point targets is 150 m. Area targets can be engaged out to 400 m.

The main user of the T-40 is the Turkish military. The T-40 is widely used on both G3 battle rifles and HK 33 assault rifles. Limited quantities have been exported. The Israeli Tavor is marketed with a slightly modified T-40 for export sales and this combination is in use with India.