The Model 12 Trench gun is available for use in both Medal of Honor classic and Underground. It is a very powerful weapon, capable of killing an enemy in 1 shot to the head or chest at close range. It's unique among the weapons that appear in both original Medal of Honor games because it has different skins in these two games. However, they still have same behavior, including sound.
In the "Panzerknacker Unleashed" mission, the shotgun bares the same skin as in the original game.
In Single player, the player only gets to use the Shotgun in 2 levels: the manor house, the assault on Fort Schmerzen,and in Breakthrough, it is found in the harbor level (incognito) laying by a crate. It does high damage at close range, but beyond that it is outclassed by other weapons due to its slow rate of fire and inaccuracy.
In Multiplayer, the M12 Shotgun is available to all factions. It is alarmingly powerful, it's damage is very high at close range. But at medium range it is likely to only heavily injure the enemy, not kill them, and the M12 will do very scarce damage at longer range. It is a devastator, and it has been so heavily used in most games, it's use has become frowned upon.
The M1912 Shotgun as it appears in Allied Assault.
The M1897 Trench Gun returns in Frontline, though this variant as opposed to the other variants, is the M1897 Trench Gun version, with a hammer at the back of the gun. It is seen in the hands of a Dutch Resistance member in Several Bridges Too Far before he is killed by multiple German snipers. It is exactly the same as the Allied Assault version, bearing the skin differences and the 8 shell capacity instead of 5. It is capable of getting a 1-hit kill on most enemies. It is usable in the missions "Needle in a Haystack" and "Several Bridges Too Far". The Frontline version probably has the tightest pellet spread radius of all shotguns in the franchise, even tighter than the ones in European Assault and Airborne (with barrel choke), so it is hard to kill enemies without aiming, something that was possible in early games. It is interesting to note that the reload time is not shell based and all 8 rounds are loaded at once, resulting in a shorter empty reload, but a theoretically longer reload when few shells have been expended.
The M1912 "Trench gun" appears once again, it is now more deadly at close range as well as long range and is quite accurate at both, things that shotguns usually lack. It is one of starting weapons in levels Operation Blindfold, Operation: V2 Silence, and can be found in level Farmhouse Liberation next to a Christmas tree.
This is a selectable weapon in Medal of Honor: Airborne. It is a very powerful weapon, with a medium rate of fire and high power, but low magazine capacity. It can be a one-hit kill even at medium-long range with the barrel choke attachment. It's primary limiting features are its large hip-fire spread and slow reload.
Barrel choke: Tighter pellet spread
Buckshot rounds: Increased damage
Bayonet: Increased melee damage and distance, kills all regular troops with one stab.
The Trench Gun returns both games. In Heroes the Trench Gun first can be picked up in the first level. Later it can be picked up in later levels as well. Since in Heroes you can't replace the M1911 with an other weapon replacing a Thompson or a BAR can be a mistakes since the Trench Gun has a short range, but it's very good for close-range fighting. It shares the same model from European Assault and the sounds as well. In Heroes 2 the Trench Gun can be seen in promotional pictures as well the box art. In game the Trench Gun first can be picked up in the City level where it's advised to replace your secondary pistol with a good close range gun. The Trench Gun has been retextured in Heroes 2 and has new sounds as well. It has a new pumping animation when firing from the hip. In both games the Trench Gun can be choosen as a starting weapon for both allied and axis soldiers.
In the original game and Underground, if killed by the shotgun at very close distance, enemies will die in very aspecial manner: the power of the pellets will throw out their head and chest so their fall bares much resemblance to a Fosbury Flip, an athletic move used by high jumpers. This can sometimes be done by a Bazooka, but you should be very careful and aim for the head.
Oddly, shotgun is the most often found weapon in original game: it is starting weapon in 10 levels( in 4.,5., and 7. mission) and is found in level Sewer Chase.
Also, if dogs are killed by a shotgun in first two games, they will die with a howl that sounds like 'pooy'
In Multiplayer for Allied Assault, the maximum ammo is 65.