Calzada Bayo CB-57

Lore & Background

The CB-57 was the final prototype in a series of rifles designed by Calzada Bayo, following the CB-51 and CB-52. All three were derivatives of the German Sturmgewehr-44, adapted for post-war use. The CB-57 was a contender against the CETME Modelo A for a Spanish military contract. Unlike the StG-44, the CB-57 lacks a pistol grip, instead using a stock that serves as the handle, similar to an SKS carbine. It also does not have a shroud over the barrel that serves as a handguard. The bolt assembly of the CB-57 is practically identical to that of the StG-44. The rifle is semi-automatic only, unlike the selective-fire StG, and uses high-capacity magazines.

Reader's Guide

The CB-57 represents a post-World War II attempt to modernize the StG-44 design for a full-power battle rifle cartridge. While the StG-44 used the intermediate 7.92×33mm Kurz round, the CB-57 was chambered for the 7.62×51mm NATO cartridge to meet NATO requirements. Earlier prototypes, the CB-51 and CB-52, had been chambered for the 8×33mm Kurz and 7.92×40mm rounds respectively. The Spanish military ultimately adopted the CETME rifle instead, leaving the CB-57 as an obscure prototype. Few StG-type designs have been produced since World War II, and the failure of the CB rifles did little to increase the popularity of similar reproduction rifles in modern calibers. Little is known about the CB rifles because the Spanish government has not released much information on their history.

Did You Know?

• The CB-57 is a derivative of the Sturmgewehr-44.
• The CB-57 lacks a pistol grip and barrel shroud, unlike the StG-44.
• Earlier prototypes were chambered in 8×33mm Kurz and 7.92×40mm.

Design & Heritage

The Calzada Bayo CB-57 emerged from the post-World War II era when numerous nations sought to build upon the advanced weaponry developed by Nazi Germany. As a direct derivative of the Sturmgewehr-44, the CB series represented Spain's attempt to modernize that iconic assault rifle concept for contemporary military use. The design retained the StG-44's core architecture while introducing notable departures: rather than the original's pistol grip, the CB-57 employed a full stock that doubled as the handle, reminiscent of an SKS carbine. It also lacked the barrel shroud that on the StG served as a handguard. Functionally, the CB rifles were restricted to semi-automatic operation, aligning them with conventional battle rifles of the period, yet they retained the high-capacity magazines that set the StG apart from most of its contemporaries. By the time the CB-57 entered the picture, its bolt assembly was virtually indistinguishable from the StG-44's, even though earlier CB prototypes had shown slight divergences. The only meaningful distinctions between the CB variants were their chamberings and a handful of minor cosmetic adjustments.

Chambering Evolution

The CB series tells a story of iterative cartridge selection as Spain's requirements shifted. The earliest prototype, the CB-51, was chambered for the original 8×33mm Kurz round that powered the StG-44, but this choice proved impractical because the ammunition was simply too scarce for real-world military application. The CB-52 then adopted the 7.92×40mm cartridge, a slightly elongated version of the 8×33mm that employed a very long, light bullet. This design was an attempt to satisfy two demanding specifications simultaneously: achieving a 1000-meter effective range while keeping recoil impulse low. The final iteration, the CB-57, abandoned these intermediate cartridges entirely in favor of the 7.62×51mm NATO round, a much more powerful full-power battle rifle cartridge. This switch was driven not by ballistic preference but by the practical necessity of meeting NATO standardization requirements. The progression from scarce German intermediate rounds to a universally available NATO cartridge underscores how geopolitical alignment ultimately dictated the CB-57's final specification.

Competition & Fate

The CB-57 was one of several prototype rifles developed for consideration by the Spanish armed forces in the aftermath of World War II. Its principal rival in the competition was the CETME Modelo A, another contender seeking the same military contract. Ultimately, Spain selected the CETME rifle for adoption, leaving the CB-57 and its predecessors unadopted and largely forgotten. Very few examples of the CB rifles were ever built, and the design never progressed beyond the prototype stage. The failure of the CB series to gain a military contract effectively sealed its fate as a historical curiosity rather than a service weapon. The Spanish government has released very little information about the history of the CB-57 and its earlier prototypes, the CB-51 and CB-52, leaving much of the design's development shrouded in uncertainty. What little is known comes from scattered references and the fact that the weapon existed as a documented prototype. The CB-57 thus stands as a creative but ultimately unsuccessful attempt to bring a StG-44-derived concept into the postwar Spanish military landscape.

Legacy & Obscurity

Few rifle designs of the StG-44 type have been produced since World War II, and the CB series represents one of the rare postwar attempts to carry that lineage forward. The ultimate failure of the CB rifles to achieve adoption did little to inspire or increase the popularity of similar reproduction rifles in modern calibers in the years that followed. The CB-57 remains a relatively obscure yet genuinely creative firearm in the annals of Spanish small-arms development. Its obscurity is compounded by the Spanish government's decision to release very little public information about the weapon's history, the development of its predecessors, or the specifics of the competition process that led to the CETME's selection. The result is a design known primarily through scattered references and the simple fact that it existed as a documented prototype. For firearms historians and collectors, the CB-57 occupies a fascinating niche: a semi-automatic, high-capacity battle rifle that married the mechanical soul of the StG-44 with NATO-standard ammunition, yet never saw a single day of military service.