The West German police units at the time lacked the precision shooting capability to effectively neutralize the terrorists to prevent the hostages being killed.

H&K was then commissioned to create a high-accuracy, large-magazine capacity, semi-automatic rifle for law enforcement and military use.

[1] The PSG1 is mechanically based on the Heckler & Koch G3 battle rifle that employs a roller-delayed blowback operating system.

"[2] The rifle has a strengthened receiver with rails welded over the channels where a retractable buttstock would slide and features numerous other upgrades and such to meet the necessities of police sniper units.

The two sliding locking rollers that hold the bolt in battery during firing are not cylindrical shaped like in normal G3 rifles, but semi-cylindrical shaped to offer a non-random more precise positioning on corresponding flat surfaces in the barrel extension locking recesses.

The PSG1 also features a low-noise bolt closing device (similar to the forward assist on many M16 rifles).

For these reasons, the PSG1A1 has been outfitted with a Schmidt & Bender 3–12×50 Police Marksman II scope, mounted on 34 mm (1.3 in) rings.

The MSG90 uses a modified version of the push pin trigger packs of H&K roller-delayed select-fire assault rifles.