Description of Related Art

The concept of caseless ammunition has long captivated firearms designers and military strategists due to its inherent advantages. The weight of the cartridge case constitutes a substantial proportion of the total ammunition weight. For military applications, this translates directly into limitations on the amount of ammunition a soldier can carry, the payload capacity of aerial platforms (manned or unmanned), and overall logistical burdens. Lighter ammunition frees up carrying capacity, enabling greater munitions supplies or other critical provisions to be transported. Furthermore, the cost of cartridge cases is a major component of ammunition production expenses, whether for commercial, recreational, professional, or governmental use. Eliminating the case promises substantial cost savings. Beyond weight and cost, the spent case requires ejection, which complicates firearm design, creates a physical signature (evidence) at the firing location, and necessitates collection or disposal.

Historically, the cartridge case, typically made of brass or steel, serves several crucial functions: it holds the primer, propellant (powder), and projectile together as a single unit; it seals the breech during firing to contain propellant gases; and it provides a robust structure for handling and feeding. Moreover, the hot cartridge case, upon ejection from the firearm, serves as an effective means of removing a significant amount of heat from the firearm's operating system, thus actively preventing heat buildup during sustained firing. However, the case also represents significant drawbacks, primarily in terms of weight, cost, and logistical complexity.

Efforts to develop caseless ammunition gained particular intensity during World War II, as nations like Germany faced increasing scarcity of critical metals, notably copper required for cartridge cases. German researchers pursued internal-propellant caseless designs, achieving some developmental progress, though not sufficient for widespread wartime production. An example of their near-production efforts included the 55 mm Maschinenkanone MK 155, which employed partially combustible cartridges. In contrast, Japan successfully deployed an aircraft-mounted autocannon, the Ho-301 40 mm, utilizing internal-propellant caseless ammunition, seeing limited combat use in the final stages of the war. Despite these wartime innovations, the use of internal-propellant caseless ammunition largely receded from mainstream weapons development after the conflict.

A recurring and significant disadvantage of internal-propellant caseless designs was the accumulation of propellant residue within the firearm's operating system. Since the propellant is entirely consumed within the chamber, its burning byproducts are not ejected with a spent case, leading to a buildup that frequently caused operational malfunctions and required extensive cleaning. To counteract this, designers often had to resort to reducing propellant charges or implementing recoilless gun solutions that vented some burning propellant rearward. Such compromises, however, inherently led to diminished muzzle velocities, often remaining subsonic (around 200–250 m/s or 660–820 ft/s). For weapons intended for horizontal fire, these low velocities severely restricted effective range and accuracy due to rapid projectile energy loss and pronounced trajectory arcs, rendering them largely unsuitable for the typical engagement distances and precision required of small arms. The reliance on such low-velocity projectiles fundamentally limited the combat utility of these caseless systems for infantry applications.

One of the most notable post-WWII endeavors in caseless firearm technology was the Heckler & Koch G11 rifle, developed by West Germany during the Cold War. This ambitious project spanned over two decades, from the late 1960s to the late 1980s, and involved significant financial investment. For instance, an initial development contract in December 1974 was valued at 20 million Deutsche Marks (DM). To provide a contemporary perspective, 20 million DM in 1974 is approximately equivalent to 7.75 million USD in 1974 (using an average exchange rate of 1 USD = 2.58 DM for 1974). Adjusting for inflation to 2025, this initial contract value alone would be over 50 million USD. The overall project's total funding over its two-decade lifespan would undoubtedly be substantially higher than this initial contract. The G11 development cost from 1974 to 1989 was 84.1 million DM (borne by the West German taxpayer), or nearly 120 million USD today. Development also left H&K with a debt of 180 million DM (1989), or nearly 250 million USD today.

The G11 featured a distinctive block of propellant with an embedded primer and projectile, engineered for complete consumption upon firing. This design offered the promise of substantial weight reduction and high rates of fire by eliminating the need for case extraction and ejection. However, the G11's innovative nature was overshadowed by significant practical obstacles that ultimately prevented its widespread adoption. A primary impediment was its profound mechanical complexity, which rendered the firearm difficult to manufacture, maintain, and disassemble for field stripping. Its intricate rotating chamber and feeding mechanisms were susceptible to fouling and demanded specialized training for military personnel, thereby undermining its combat readiness. Furthermore, the G11 was entirely reliant on specialized, proprietary caseless ammunition, which severely constrained its logistical flexibility and compatibility with existing supply chains. The G11 specialized cartridges were prone to crack or chip, necessitating careful handling and packaging. One practice to accommodate the delicacy of the ammunition was to load magazines using specialized clips of ammunition held in packages similar to stripper clips. The propellant itself also demonstrated a susceptibility to "cook-offs"—premature ignition caused by heat accumulation within the chamber—a persistent thermal management challenge for caseless systems where the propellant directly contacts residual heat from prior firings. Crucially, the impossibility of modifying the G11 to use NATO-standard ammunition components was a decisive factor that ultimately led to the project's cancellation.

Another approach to caseless firing emerged with the Daisy V/L rifle, introduced by the airgun manufacturer Daisy in 1968. This system employed a .22 caliber (5.5 mm) low-powered caseless round that uniquely lacked a primer and relied on an external propellant. The rifle itself functioned primarily as a spring-piston air rifle. When used with the V/L ammunition, the kinetic energy from the piston's compression generated sufficient heat in the air behind the caseless round to ignite the propellant, which then provided the majority of the firing energy. While an interesting innovation, the Daisy V/L system was inherently limited by its low power output, its dependence on a specialized external-propellant design, and the constraints of its air-piston ignition method, which precluded its application in high-performance or military-grade firearms. Its unique ammunition, though conceptually simple, offered no integration with conventional ammunition components.

Despite these varied attempts, including designs with combustible cases or advanced propellant formulations, none fully resolved the fundamental issues of excessive complexity, reliance on specialized ammunition, or reliable thermal management to prevent cook-offs during sustained operation. The enduring need has been for a caseless firearm system that is robust, dependable, straightforward to operate and maintain, compatible with readily available, standard components, and capable of effectively managing thermal challenges.

BrashZero addresses these long-standing problems by providing a novel caseless operating system that entirely dispenses with the need for a pre-packaged cartridge case. BrashZero achieves this while utilizing standard, NATO-Spec ammunition components (primers, powders, projectiles), thereby eliminating the logistical and cost burdens associated with specialized ammunition. Furthermore, BrashZero incorporates innovative heat management and operational principles that enhance reliability, reduce complexity, and minimize the risk of cook-offs, offering a significant advancement over prior art caseless firearm designs.