Where hammer-forged rifle barrels originated

Cold hammer forging of rifled barrels is a German 1930s industrial process. A short, oversize-bored blank is driven over a hardened mandrel that carries the reverse of the rifling. Radial hammers then beat the steel onto the mandrel. The tube lengthens, the bore is work-hardened, and the rifling is formed without cutting. That much is not in dispute. Who first applied it to military rifle and machine-gun barrels is.

What the popular BLM story actually says

English-language pages, including the English Wikipedia entry on Berlin-Lübecker Maschinenfabrik, often state that BLM “invented the hammer forged barrel process.” That claim is repeated on collector sites and is usually traced to post-1945 Allied reporting and later internet summaries. It is not supported by the German Wikipedia article on the same firm. The German account says BLM’s development work aimed at speeding production and that the plant produced an automatic barrel-straightening machine. It does not credit BLM with inventing cold hammer forging.

BLM was founded in the mid-1930s (often dated 1934–36), funded in part by the Heereswaffenamt, and began Kar98k work around 1936. It was a new plant in Lübeck, not an old barrel-making centre. Low early Kar98k output is consistent with a start-up factory, not with being the unique source of a new national process.

American technical writing is more cautious. Papers associated with James Higley and Vern Briggs, and later summaries on WeaponsMan and Accurate Shooter, place the technology in Germany before or during the late 1930s, often linking it first to machine-gun barrel demand (MG34/MG42 barrel life and replacement rates), then to wider use. Dates such as “1934” or “1939” appear in trade and hobby literature; they are not tied to a single surviving patent that names BLM as inventor.

A stronger paper trail exists for Gustav Appel Maschinenfabrik. Commentators who have looked at patents argue that Appel developed cold radial hammering (including work on small tubes such as hypodermic needles) before the war, then applied related machines to barrels. Bruno Kralowetz, later founder of GFM in Steyr (1945–46), is associated with that circle. GFM’s first commercial barrel-forging machines are generally dated around 1950. That postwar Austrian industry explains why modern hammer-forging machines are so often “GFM,” not “BLM.”

Verdict on BLM: BLM may have used or even refined hammer forging in wartime production. The statement that BLM invented it rests mainly on one strand of English secondary literature and is not corroborated by the German company history or by the Appel–Kralowetz–GFM machine lineage.

What the Suhl hypothesis can and cannot prove

Suhl was Germany’s historic small-arms district. J.P. Sauer & Sohn, Haenel, Simson/BSW and many barrel and parts shops were there. Schilling & Krämer (Suhl) is well documented as a specialist machine-tool maker for the gun trade from the 1860s: barrel-boring machines, lathes, milling machines. Period notices say Suhl rifle works ordered almost all their machines from that firm, and that American visitors in the 1870s studied Schilling & Krämer equipment. A 1939 Sauer purchase of rifling-related machinery from Schilling & Krämer is plausible and consistent with that tradition. It does not, by itself, prove that Schilling & Krämer designed the first cold-hammer rifling forge in 1935.

GERAP (Geräte- und Apparate-Handelsgesellschaft) is a real Heereswaffenamt procurement vehicle used in rearmament. Central buying of machine tools and issue to several plants is historically reasonable. Public sources do not yet show a complete chain: “GERAP ordered hammer-forging machines from Schilling & Krämer in 1935 and issued them to every Kar98k maker by 1939.”

The slug study (lead slugs driven through dated Kar98k and MG barrels; sloped groove shoulders taken as forged, square shoulders as cut) is a useful workshop method and matches what other researchers have looked for on 1930s German MG barrels. If a run of Sauer-marked 1936 barrels consistently shows forged-type impressions, that is evidence of early adoption at Sauer, not automatic proof that Suhl invented the process. Barrels were subcontracted; codes, dates and later replacements must be controlled. Czech Brünn plants staying with cut rifling is consistent with existing broach/cut capacity, not a refutation of German hammer forging.

Verdict on Suhl: Suhl had the skills, the machine-tool firms, and at least one major barrel maker (Sauer) that could have been an early user. “Pioneered in Suhl in 1935” remains a working hypothesis, stronger than the BLM invention story, but not a closed case.

What can be stated as fact

1. Cold hammer forging of rifled barrels is a German 1930s development, scaled under rearmament and wartime barrel demand.

2. The BLM-as-inventor story is overstated and poorly sourced next to German company history and the Appel/GFM machine line.

3. Suhl was the natural place for early adoption; Schilling & Krämer supplied gun-plant machinery; Sauer was a major barrel source. Early Sauer forged barrels, if confirmed on a large dated sample, would show use by 1936, which would pre-date BLM at full scale.

4. After 1945 the industrial future of the process sat with GFM (Steyr) and related Austrian/German machine builders, not with Lübeck.

5. By about 1938–39 hammer-forged barrels appear widely enough in German service rifles that “all German Kar98k makers by 1939” is a fair working summary, with occupied Czech plants as the usual exception.

Conclusion

Hammer-forged rifling did not originate as a unique BLM Lübeck invention in the sense popular English pages claim. It grew out of German cold-forging machine practice in the 1930s. Suhl is a better candidate for early rifle-barrel use than Lübeck is for invention. The inventors of the machines are more credibly sought in firms such as Gustav Appel and the engineers who later formed GFM, not in a single Kar98k assembly plant.

Research notes and slugged barrels by MC. Compare English Wikipedia on BLM with the German company article, Appel/GFM machine history, and a dated Sauer barrel sample before repeating a catalogue caption.