The first MP5 models used a double-column straight box magazine, but since 1977, slightly curved, steel magazines are used with a 15-round capacity (weighing 0.12 kg) or a 30-round capacity (0.17 kg empty).

The adjustable iron sights (closed type) consist of a rotating rear diopter drum and a front post installed in a hooded ring.
The rear sight is mechanically adjustable for both windage and elevation with the use of a special tool, being adjusted at the factory for firing at 25 metres (27 yd) with standard 8 grams (123 gr) FMJ 9×19mm NATO ammunition.
The rear sight drum provides four apertures of varying diameters used to adjust the diopter system, according to the user's preference and tactical situation.
Changing between apertures does not change the point of impact down range.
For accurate shooting the user should select the smallest aperture that still allows an equal circle of light between the rear sight aperture and the outside of the front sight hood ring.

The MP5 has a hammer firing mechanism.
The trigger group is housed inside an interchangeable polymer trigger module (with an integrated pistol grip) and equipped with a three-position fire mode selector that serves as the manual safety toggle.
The "S" or Sicher position in white denotes weapon safe, "E" or Einzelfeuer in red represents single fire, and "F" or Feuerstoß (also marked in red) designates continuous fire.
The SEF symbols appear on both sides of the plastic trigger group.
The selector lever is actuated with the thumb of the shooting hand and is located only on the left side of the original SEF trigger group or on both sides of the ambidextrous trigger groups.
The safety/selector is rotated into the various firing settings or safety position by depressing the tail end of the lever.
Tactile clicks (stops) are present at each position to provide a positive stop and prevent inadvertent rotation.
The "safe" setting disables the trigger by blocking the hammer release with a solid section of the safety axle located inside the trigger housing.

The non-reciprocating cocking handle is located above the handguard and protrudes from the cocking handle tube at approximately a 45° angle.
This rigid control is attached to a tubular piece within the cocking lever housing called the cocking lever support, which in turn makes contact with the forward extension of the bolt group.
It is not however connected to the bolt carrier and therefore cannot be used as a forward assist to fully seat the bolt group.
The cocking handle is held in a forward position by a spring detent located in the front end of the cocking lever support which engages in the cocking lever housing.
The lever is locked back by pulling it fully to the rear and rotating it slightly clockwise where it can be hooked into an indent in the cocking lever tube.
The first MP5 models used a double-column straight box magazine, but since 1977, slightly curved, steel magazines are used with a 15-round capacity (weighing 0.12 kg) or a 30-round capacity (0.17 kg empty).
The adjustable iron sights (closed type) consist of a rotating rear diopter drum and a front post installed in a hooded ring. The rear sight is mechanically adjustable for both windage and elevation with the use of a special tool, being adjusted at the factory for firing at 25 metres (27 yd) with standard 8 grams (123 gr) FMJ 9×19mm NATO ammunition. The rear sight drum provides four apertures of varying diameters used to adjust the diopter system, according to the user's preference and tactical situation. Changing between apertures does not change the point of impact down range. For accurate shooting the user should select the smallest aperture that still allows an equal circle of light between the rear sight aperture and the outside of the front sight hood ring.
The MP5 has a hammer firing mechanism. The trigger group is housed inside an interchangeable polymer trigger module (with an integrated pistol grip) and equipped with a three-position fire mode selector that serves as the manual safety toggle. The "S" or Sicher position in white denotes weapon safe, "E" or Einzelfeuer in red represents single fire, and "F" or Feuerstoß (also marked in red) designates continuous fire. The SEF symbols appear on both sides of the plastic trigger group. The selector lever is actuated with the thumb of the shooting hand and is located only on the left side of the original SEF trigger group or on both sides of the ambidextrous trigger groups. The safety/selector is rotated into the various firing settings or safety position by depressing the tail end of the lever. Tactile clicks (stops) are present at each position to provide a positive stop and prevent inadvertent rotation. The "safe" setting disables the trigger by blocking the hammer release with a solid section of the safety axle located inside the trigger housing.
The non-reciprocating cocking handle is located above the handguard and protrudes from the cocking handle tube at approximately a 45° angle. This rigid control is attached to a tubular piece within the cocking lever housing called the cocking lever support, which in turn makes contact with the forward extension of the bolt group. It is not however connected to the bolt carrier and therefore cannot be used as a forward assist to fully seat the bolt group. The cocking handle is held in a forward position by a spring detent located in the front end of the cocking lever support which engages in the cocking lever housing. The lever is locked back by pulling it fully to the rear and rotating it slightly clockwise where it can be hooked into an indent in the cocking lever tube.
Heckler & Koch MP5