Knorr-Bremse FG 42 prototype: an undocumented mystery rifle at Springfield Armory

Key points: Knorr-Bremse FG 42 prototype

• The rifle sits in the Springfield Armory National Historic Site reference collection with no documented accession — the catalog attributes it to Knorr-Bremse, but nobody knows where that attribution came from or how the gun reached Springfield.
• Its characteristics place it in late-war Germany, though McCollum cannot say whether it was recovered from a captured factory or arrived on the Mauser train that brought other late-war German prototypes into the collection.
• Calling it an FG 42 prototype is itself odd: Knorr-Bremse was not among the six companies invited to the FG 42 program, only Rheinmetall and Krieghoff submitted designs, and both of those guns are accounted for — so there is no missing prototype for this to be.
• It nonetheless reads as FG 42 throughout: within the overall length limit of a Kar 98k despite being self-loading, a side-mounted magazine well sized for full-length 8mm Mauser rather than 8mm Kurz, and a stamped pistol grip assembly built the way FG 42 fire control grips were.
• The most telling detail visible only in person is the top of the barrel extension, drilled with two vertical holes that suggest a roller-locked action along MG 42 lines; the rollers, bolt and carrier are all absent, leaving the theory untestable.
• Other construction notes: a spot-welded two-piece stamped receiver McCollum calls sophisticated for the period, a milled rear sight block welded to the stamping, a non-adjustable integral front sight, a gas block and probable short-stroke piston under a pinned front cap, and a charging handle that latches forward so it does not reciprocate.
• No markings of any kind turned up, including the CSM ordnance code Knorr-Bremse should carry; the hammer appears unhardened and firing-pin dimpled, the trigger and pins are seized, and McCollum stops short of further disassembly rather than risk damage.

About this Gun Review video

Knorr-Bremse FG 42 prototype, examined hands-on: Ian McCollum pulls an undocumented late-war German rifle from the Springfield Armory reference collection and shows what the archival photographs never did. It is a stamped, side-feeding design built to FG 42 specifications by a company never invited to the FG 42 trials, and its accession history is blank. He walks the perforated muzzle device, integral front sight, latching charging handle, and a barrel extension drilled for what look like MG 42-style locking rollers — then lists what is missing: bolt, carrier, stock, markings.

Transcript: Knorr-Bremse FG 42