When the German military started looking for a self-loading rifle in the late 1930s, they had a pretty strict set of requirements. Most significantly, the rifles could not have gas ports or recoiling barrels, could not have moving parts on top of the action, and had to be capable of being operated manually with a bolt handle like a bolt action Mauser. Four companies tried to get into the resulting rifle trials, but only two were able to build good enough guns to get contracts for field trials. These were Walther and Mauser. Walther ended up winning the competition (largely because they ignored several of the RFP requirements) and their rifle became the Gewehr 43. Mauser stuck to the requirements with their Gewehr 41(M), and it cost them the competition.