Wikipedia
StG 45(M)
View on WikipediaThe StG 45(M) (abbreviation of Sturmgewehr 45, "Assault Rifle 45") sometimes referred to as the MP 45(M), was a prototype assault rifle developed by Mauser for the Wehrmacht at the end of World War II, using an innovative roller-delayed blowback operating system. It fired the 7.92×33mm Kurz (or "Pistolenpatrone 7.9mm") intermediate cartridge at a cyclic rate of around 450 rounds per minute.
Key Information
Overview
[edit]

The origin of this rifle can be traced back to the final years of World War II when Mauser engineers at the Light Weapon Development Group (Abteilung 37) at Oberndorf am Neckar designed the MKb Gerät 06 (Maschinenkarabiner Gerät 06 or "machine carbine device 06") prototype assault rifle chambered for the intermediate 7.92×33mm Kurz cartridge, first with the Gerät 06 model using a roller-locked mechanism which was unique for being gas operated, as opposed to recoil operation, originally adapted from the MG 42 machine gun, but with a fixed barrel and conventional gas-actuated piston rod.[2] After observing bolt-bounce during firing trials of the roller locked Gerät 03 prototype semi-automatic rifle Dr. Karl Maier, one of Mauser's scientists at the time,[3] realized that with careful attention to the mechanical ratios, the gas system could be omitted.[4][5] The resultant weapon, the Gerät 06H (the "H" suffix is an abbreviation for halbverriegelt or "half-locked") was assigned the designation StG 45(M) (Sturmgewehr 45(M)).
Though appearing simple, developing the roller-delayed blowback firearm action was a hard technical and personal effort, as German engineering, mathematical and other scientists had to work together on a like-it-or-not basis led by Ott-Helmuth von Lossnitzer, the director of Mauser Werke's Weapons Research Institute and Weapons Development Group. Experiments showed roller-delayed blowback firearms exhibited bolt-bounce. To counter bolt- bounce the perfect angle choice on the nose of the bolt head had to be found. Mathematician Dr. Karl Maier provided analysis of the components, assemblies in the development project. In December 1943 Maier came up with an equation that engineers used to change the angles in the receiver to 45° and 27° on the locking piece relative to the longitudinal axis solving the bolt-bounce problem. With these angles the geometrical transmission ratio of the bolt carrier to the bolt head became 3:1, so the rear bolt carrier was forced to move three times faster than the bolt head. The rearward forces on the bolt carrier and receiver were 2:1. The force and impulse transmitted to the receiver increases with the force and impulse transmitted to the bolt carrier. Making the bolt carrier heavier lessens the recoil velocity. For Mausers Gerät 06H/StG 45(M) project Maier assumed a 120 g bolt head and 360 g bolt carrier (1 to 3 ratio). However, the design required that the bolt started moving while the bullet was still in the barrel and the spent case fully pressurized. Using traditionally cut chambers resulted in separated cartridge case heads during testing. This problem was solved by cutting 18 longitudinal gas relief flutes in the chamber. Fluting the end of the chamber allowed combustion gasses to float the neck and front of the cartridge case providing pressure equalization between the front outer surface of the cartridge case and its interior. During the process, the front cartridge case would typically show blackened, longitudinal scorch marks around the diameter of the case which was characteristic for later roller-delayed blowback-operated small arms, which also used the fluted chamber principle.
The roller-delayed blowback firearm action was patented by Mauser’s Wilhelm Stähle and Ludwig Vorgrimler.
Like the German FG 42 battle rifle/automatic rifle and the Sturmgewehr 44 assault rifle, the StG 45(M) was one of the first inline firearms incorporating a "straight-line" recoil configuration. This layout places both the center of gravity and the position of the shoulder stock nearly in line with the longitudinal axis of the barrel bore, a feature increasing controllability by reducing muzzle rise during burst or automatic fire.[6] The elevated sight line over the bore axis layout was also adopted from these designs as it helps to extend the "battle zero" range. The current trend for elevated sights and flatter shooting higher-velocity intermediate cartridges in assault rifles is in part due to a desire to further extend the maximum point-blank range, which makes such a rifle easier to use.[7][8]
The StG 45(M) was intended to replace the Sturmgewehr 44 assault rifle, because the latter was rather expensive and time-consuming to produce. Compared to the StG44's cost of 70 ℛ︁ℳ︁, the StG45(M)'s calculated cost was 45 ℛ︁ℳ︁. Like the Sturmgewehr 44 the weapon made extensive use of (for the 1940s) advanced cost-saving pressed and stamped steel components rather than machined parts. Parts kits for only 30 complete rifles were produced before the war ended. The StG 45(M) had an elevated iron sights line over the bore axis in part to optimize the maximum point-blank range of the compared to full-power rifle cartridges modest external ballistic performance of the 7.92×33mm Kurz cartridge, ergonomics and recoil management.
While the StG45(M) was intended to use the same 30-round magazine as its predecessor, the rifle is commonly pictured with the 10-round magazine designed for the Volkssturmgewehr. The shorter magazine was used by Mauser engineers during testing, as its lower profile was easier to use when test-firing at the Mauser facility range.
The Bundeswehr Museum of German Defense Technology in Koblenz has one of these specimen in its collection.
Post–World War II developments
[edit]
The German technicians involved in developing the Sturmgewehr 45 continued their research in France at CEAM. The StG45 mechanism was modified by Ludwig Vorgrimler and Theodor Löffler at the Mulhouse facility between 1946 and 1949. Three versions were made, chambered in .30 Carbine, 7.92×33mm Kurz as well as the 7.65×35mm cartridge developed by Cartoucherie de Valence and adopted in 1948. A 7.5×38mm cartridge using a partial aluminium bullet was abandoned in 1947. Löffler's design, designated the Carabine Mitrailleuse Modèle 1950, was retained for trials among 12 different prototypes designed by CEAM, MAC, and MAS. Vorgrimler later went to work at CETME in Spain and developed the line of CETME automatic rifles.
Germany eventually purchased the licence for the CETME design and manufactured the Heckler & Koch G3 as well as an entire line of weapons built on the same system, one of the most famous being the MP5.
A few other post–World War II weapons used the roller-delayed locking system, such as the SIG SG 510.
See also
[edit]References
[edit]- ^ a b c d e f g h i j Götz, Hans Dieter (1990). German Military Rifles and Machine Pistols. Atglen, Pennsylvania: Schiffer Publishing. p. 220. ISBN 978-0-88740-264-7.
- ^ Senich, Peter R. (1987). The German Assault Rifle: 1935–1945. Boulder, Colorado: Paladin Press. p. 153. ISBN 978-0-87364-400-6.
- ^ Forgotten Weapons (2012-11-19). "Last Ditch Innovation: The Development of the Gerat 06 and Gerat 06H Rifles". YouTube. Retrieved 2017-11-13.
- ^ McCollum, Ian (January 1, 2013). "Do You Know Your HK's Parents?". The Firearm Blog.
- ^ Senich (1987), p. 158.
- ^ Senich (1987), p. 239.
- ^ "An Improved Battlesight Zero for the M4 Carbine and M16A2 Rifle". AR15.com. Retrieved 2007-09-11.
- ^ "TM 9-1005-319-10 (2010) - Operator's Manual for Rifle, 5.56 MM, M16A2/M16A3/M4 (Battlesight Zero pages 48-55)" (PDF). AR15.com. Retrieved 2014-06-03.
External links
[edit]- McCollum, Ian (January 1, 2013). "Do You Know Your HK's Parents?". The Firearm Blog.
- Forgotten Weapons (2012-11-19). "Last Ditch Innovation: The Development of the Gerat 06 and Gerat 06H Rifles". YouTube.
- "StG45 at an IPSC 3-Gun Match (Video)". Forgotten Weapons. July 1, 2012.
Grokipedia
StG 45(M)
View on GrokipediaDevelopment
Origins and Design Requirements
The Sturmgewehr 44 (StG 44), while revolutionary as the first mass-produced assault rifle, proved costly and complex to manufacture, with each unit requiring approximately 70 Reichsmarks and extensive machining that strained Germany's dwindling industrial resources in late World War II.[3] This high production cost, combined with the weapon's intricate gas-operated mechanism and milled components, prompted the Wehrmacht to seek a more economical alternative using simplified stamped-metal construction to enable faster output under severe material shortages.[5] The StG 44 served as the baseline predecessor, influencing the new design's overall layout and intermediate cartridge while highlighting the urgent need for cost reductions to sustain infantry armament amid escalating Allied advances.[3] In mid-1944, the Wehrmacht issued specifications for a select-fire assault rifle weighing under 5 kg to improve soldier mobility, chambered in the 7.92×33mm Kurz intermediate cartridge for balanced power and controllability, and equipped with a high-capacity 30-round detachable box magazine compatible with existing StG 44 magazines.[6] The design was required to achieve an effective range of 300-400 meters, prioritizing semi-automatic accuracy at longer distances and full-automatic fire for close-quarters suppression, all while targeting a production cost below 60 Reichsmarks per unit to address wartime economic pressures.[2] Development of the StG 45(M) was led by the Mauser Werke facility in Oberndorf, where engineers focused on innovative mechanisms to meet these demands without compromising reliability.[7] Wilhelm Stähle served as the primary engineer, co-filing patents for the roller-delayed blowback system with Ludwig Vorgrimler, which promised simpler construction using fewer parts.[3] The project initiated in mid-1944, evolving from earlier Mauser prototypes like Gerät 06, as resource shortages intensified and the need for rapid weapon production grew desperate in the final months of the war.[5]Evolution from Prototypes
The development of the StG 45(M) began with the Gerät 06 prototype, a gas-operated, roller-locked assault rifle chambered in 7.92×33mm Kurz, designed by Mauser engineers including Ludwig Vorgrimler to meet wartime production demands for a simplified Sturmgewehr successor to the StG 44.[8] During testing, the Gerät 06 exhibited bolt bounce issues prior to full lockup, prompting analysis by Mauser scientist Dr. Carl Maier, who determined that the roller mechanism could function effectively in a delayed blowback configuration without the gas system, provided the bolt carrier-to-bolt head weight ratio was optimized to 3:1.[9] This insight led to the evolution into the Gerät 06H variant, which abandoned the gas piston entirely in favor of roller-delayed blowback to enhance reliability and reduce manufacturing complexity.[3] To further streamline production and achieve cost targets around 45 Reichsmarks per unit, Mauser shifted to a stamped sheet-metal receiver construction, minimizing machined components through welded steel stampings that maintained structural integrity while cutting fabrication time.[2] The bolt carrier was designed at approximately 360 grams and the bolt head at 120 grams, precisely achieving the 3:1 mass ratio calculated by Maier to ensure the rollers delayed bolt opening until chamber pressure safely dropped, preventing premature extraction failures.[9] Additional refinements included the incorporation of a fluted chamber, with longitudinal grooves that allowed residual propellant gases to flow around the spent cartridge case, facilitating reliable extraction in the absence of primary extraction mechanisms typical of gas-operated systems.[7] Experiments with stock configuration also addressed controllability, incorporating an inline design where the bore axis aligned closely with the shoulder stock to minimize muzzle rise during full-automatic fire.[3] The roller-delayed blowback system itself was formalized in a 1944 patent filed by Wilhelm Stähle and Ludwig Vorgrimler, detailing the mechanism's operation in both semi-automatic and full-automatic modes through roller engagement that leveraged recoil forces for controlled cycling.[3] These iterative modifications from the Gerät 06 prototypes culminated in the StG 45(M), prioritizing simplicity and mass-producibility amid escalating resource shortages.Design and Features
Operating Mechanism
The StG 45(M) utilized a roller-delayed blowback operating system, featuring two cylindrical rollers mounted in the bolt head that locked into recesses within the receiver's trunnion. This design delayed the bolt's rearward movement by leveraging the recoil impulse to create a mechanical disadvantage, where the initial force was primarily absorbed by the heavier bolt carrier rather than the lighter bolt body itself, ensuring chamber pressure dropped to safe levels before extraction began. Unlike gas-operated systems, this mechanism required no gas port, piston, or tapping into the barrel, simplifying the internal layout.[10][3] In the firing cycle, upon ignition of the cartridge, the expanding gases propelled the bullet forward while the recoil drove the bolt carrier rearward against the locked rollers. An angled locking piece or wedge in the carrier initially held the rollers extended outward, resisting immediate unlocking; as the carrier continued moving, the rollers were forced to cam inward into the bolt head, disengaging from the trunnion after a precisely timed delay. This allowed the bolt to rotate slightly and extract the spent casing, with fluted chambers in early prototypes assisting in residue clearance and reliable ejection by venting gases around the case. The empty case was then ejected, and the recoil spring returned the carrier forward, stripping a new round from the magazine and resetting the rollers for the next cycle.[10][8][3] The rifle supported select-fire operation through its trigger group, enabling semi-automatic mode for controlled shots or full-automatic mode for sustained fire, with a cyclic rate of approximately 450 rounds per minute. This functionality was achieved via a selector switch that altered the sear engagement, allowing the bolt carrier to cycle continuously in automatic fire without additional complexity.[3][10] Compared to the gas-operated StG 44, the roller-delayed blowback system offered significant advantages in simplicity, with fewer moving parts—eliminating the gas piston and related components—and enhanced compatibility with stamped steel construction for mass production. It also contributed to a lighter overall mechanism, reducing manufacturing time and costs while maintaining reliability under combat conditions. This approach marked an evolutionary shift from earlier gas-operated prototypes, prioritizing mechanical efficiency.[8][3][10]Construction and Components
The StG 45(M) featured a stamped sheet-steel receiver designed for economical mass production, utilizing simple forming and welding techniques to minimize machining requirements. This construction approach, combined with other stamped components for the furniture and external fittings, allowed for a lighter and more scalable build compared to earlier designs. The roller-delayed blowback system played a key role in enabling this stamped construction by eliminating the need for a complex gas-operated mechanism.[3][5] The rifle incorporated a fixed wooden stock with an inline configuration, aligning the bore, stock, and center of gravity to reduce recoil torque and enhance shooter control during firing. Ergonomic elements included an angled pistol grip for improved handling and a selective-fire safety lever positioned on the left side of the receiver, allowing toggling between semi-automatic and full-automatic modes. Prototypes explored options like a folding metal buttstock for compactness, though the standard wartime configuration retained the wooden fixed stock.[3][5] Key components emphasized simplicity and compatibility with existing systems. The StG 45(M) used a detachable box magazine, typically a 10-round version for testing, but was designed to accept the 30-round magazines from the StG 44 for operational flexibility. Sights consisted of an adjustable tangent rear sight graduated to 600 meters, with a hooded post front sight, providing precise aiming over the inline barrel axis.[11] An adjustable gas regulator was included in early prototypes but rendered unnecessary in the final roller-delayed blowback iteration.[3][5] Overall, the design achieved significant cost and production efficiencies, with an estimated manufacturing cost of 45 Reichsmarks—about 65% of the StG 44's 70 Reichsmarks—through a reduced parts count and streamlined assembly, potentially halving production time to around 7.4 hours per unit. This modular approach prioritized wartime scalability while maintaining reliability.[3][12]Specifications
Physical Characteristics
The StG 45(M), developed by Mauser as a late-World War II assault rifle prototype, featured a compact design optimized for the assault role, with an inline stock configuration that enhanced ergonomics by aligning the barrel with the shooter's shoulder to minimize muzzle rise during firing.[3][13] Key physical specifications of the StG 45(M) included an overall length of approximately 900 mm when unloaded, with a barrel length of 400 mm.[13][14] The rifle's empty weight varied between 3.7 kg and 4.0 kg across prototypes and sources, reflecting minor design iterations in materials and components.[15][1][13] It was chambered in the 7.92×33mm Kurz intermediate cartridge, with rifling consisting of four right-hand grooves optimized for stabilizing the lighter, shorter projectile of this round.[13][16]| Specification | Details |
|---|---|
| Overall Length | 900 mm (unloaded) |
| Barrel Length | 400 mm |
| Weight (empty) | 3.7–4.0 kg |
| Caliber | 7.92×33mm Kurz |
| Magazine Capacity | 30 rounds (standard, compatible with StG 44 magazines); 10-round experimental variant |
| Rifling | 4 grooves, right-hand twist |