From The TimeSplitters Wiki

Shotgun
Ammo	2/40
Fire Rate bullets per sec/cartridge time	2 or 3 sec per shot
Reload Time	About 15 sec
Damage (per Single Shot) Head/Body/Leg	Close Range = Instant Kill Faraway = 50-75% Damage
Type	Shotgun
Zoom	N/A
Primary Fire	Fires one shotgun shell
Secondary Fire	When held, fires both shotgun shells
Games	All

The Shotgun is a very powerful weapon, but it can only hold 2 rounds in its chamber at a time. This means that you can only fire twice before you have to reload. The Shotgun is extremely effective at close range. A close-up shot to the head is almost always an instant kill. Before you go into any engagement with an enemy, make sure you have your 2 shots loaded. Reloading is faster when engaged manually, so always try to reload when not in the action. The time spent reloading is when you are most vulnerable since the reload time is so long. You should move in as close as you can before you fire, and move around in a random pattern by strafing while you reload. This makes you much harder to hit.

The Shotgun is less effective when fired from midrange, and nearly useless when fired from long range, so always get as close to your enemy as you can for maximum effectiveness.

The Shotgun x2 can mince opposition, with four shotgun rounds fired in little over a second. Even most armoured targets cannot withstand more than two vollies.

The Shotgun has appeared in every TimeSplitters game so far.

It's worth mentioning that the Future Perfect shotgun has the longest reload time because the reload animation of ejecting the empty shells and reloading appears onscreen, whereas in the previous TimeSplitters games the gun is reloaded simply by lowering the gun offscreen. However, in "panic situations" it's possible to fire one shot off before both barrels have loaded, interrupting the reloading sequence. After firing off the shot, the reloading recommences.

Trivia

A small glitch in TSFP occurs if you reload while one shell is still in the Shotgun. The Shotgun empties its empty shell and reloads, yet when the first shell is put in, the ammunition counter says "2/2".