Otto Morawietz describes the events as follows, which makes the existence of MG ammunition from 1891 quite plausible:
Two Maxim machine guns were bought, firing the M1871 black powder cartridge.
In December, Gardner (manually driven) and said Maxim machine guns were tested. Maxim came out as superior. It was decided to modify both for firing the new smokeless 7.9 mm Patrone 88.
Trials of the Gardner were terminated, because it could not be made to work with Patrone 88.
But also the Maxim, as modified by Maxim himself and later in Germany (by Gewehr-Prüfungskommission) created an endless stream of ruptured cases even with special ammunition. The need of a special ammunition different from rifle ammunition was considered a serious drawback.
In March it was decided to terminate all trials with machine guns, because no solution seemed possible.
After that, for two and a half years there was no testing activity by the army.
During this hiatus, Ludwig Loewe (to become DWM) obtained a license for Maxim guns and sold some to the German navy. GPK managed to develop a special machine gun cartridge.
After British Admiral Commerrell had successfully demonstrated the Maxim “light” machine gun to Kaiser Wilhelm (during his annual summer trip to Norway), the latter ordered the army to resume work on machine guns.