If you look at a Gerat 06H and squint really hard, you can almost see and HK91. Ok, only if you have some imagination – but the two are intimately related. The Gerat (“Device”) 06H was the first rifle to use just a roller locking delayed blowback action, and its designers would go on to develop the CETME and HK91 series of rifles.
The gun started life at Mauser in late WWII, where the goal was to develop a cheaper alternative to the StG44 assault rifle. The initial design (the Gerat 06) used rollers to lock the action, and a gas pistol to operate. It was determined that the rollers alone could function as a delayed blowback system, eliminating the need for a gas piston.
Only a few were made, and the design was later adopted as the StG45, but the war ended before it could be put into serious production.It would have used the same 30-round magazines and 7.92×33 cartridge as the Sturmgewehr 44.
Despite its crude manufacture, care and thought went into its layout. It is comfortable to shoot, has well positioned controls (better than the HK91, for sure), and is light and easy to shoot. Given a similar amount of development and refinement, I believe the Gerat 06H/StG45 could be a combat rifle every bit the equal of the AR15. Better, in many ways.
You can see all the photos we have at the Gerat 06H page in the Vault. Unfortunately this example is incomplete, but it is still a very interesting piece.