Complex sentence: The weapon was originally designed for use with the Schiessbecher device for firing rifle grenades (standard on the Kar 98k as well) and the Schalldämpfer suppressor, however these accessories were deemed unsuccessful in tests and were dropped even before the rifle made it to serial production.
Split into simpler sentences: The weapon was originally designed for use with the "Schiessbecher" device for firing rifle grenades (standard on the "Kar 98k" as well) and the "Schalldämpfer" suppressor. However these accessories were deemed unsuccessful in tests and were dropped even before the rifle entered serial production.