The Caseless Conundrum New Generation Assault Rifle

By Paul Evancoe For USMilitary.com

A primary goal of the Army?s Program Executive Office ? Soldier (PEO Soldier), the office responsible for new DoD man-portable weapons, is to reduce the soldier?s load. Weight factors into everything from the soldier?s assault rifle, to the ammunition quantity he carries, to his kit. There have been several initiatives to replace brass-case ammunition with lighter weight caseless ammunition, even polymer-case ammunition that can be fired from existing military weapons. While it may appear plausible, accomplishing it is a challenging battle with material construction, thermodynamics and the unsurpassable laws of physics.

Replacing the existing battle rifle with a completely new generation assault rifle based upon caseless ammunition has political, fiscal and physical challenges. NATO interoperability is required by law and it is unlikely that every member country would replace its war fighting arsenal with a common caseless ammunition-type weapon. Secondly, even if NATO would unanimously agree to adopt such a replacement weapon (and by treaty unanimous member-nations agreement is required), there are other limiting factors averting their departure from conventional military weapons and ammunition.

There have been caseless prototypes built.

There have been several attempts at introducing new weapons that use caseless ammunition. One of the better known, the G-11, was developed by the renowned German arms manufacturer, Heckler and Koch. The G-11 was on the cutting edge of caseless ammo design and yet it failed to catch on, never going into full production. One reason was because DoD has never, and probably never will adopt a bullpup-style assault rifle. DoD has several logically-valid reasons for taking this position so any ?new? weapon will need to have a more traditional ergonomic design with the magazine located in front of the trigger. Another reason was that the G-11 fired radically different non-standard, non-milspec caseless ammunition and even in a perfect world, adding another ammunition type to the military?s inventory takes many years, again requiring unanimous agreement from every NATO member.

In addition, reliability concerns and supply issues associated with the radically new G-11 trumped all. HK is a German company and their gun would need to be manufactured in the U.S. for the U.S. to adopt it as DoD?s main stream battle rifle. So would its ammunition, and more than one manufacturer would be required. Lake City, the government?s primary manufacturer of small arms ammunition, was already at full production capacity. That meant expanding Lake City and investing in new tooling, or contracting someone else to supply caseless ammunition. Neither option was seen as a cost effective justification for replacement of metallic-cased ammunition or existing in-service assault weapons.

Most importantly, no requirement for a new assault rifle existed. Expensive research, development, testing and evaluation could not be justified without a valid requirement. The acceptance challenge for this radical new assault rifle became expensively daunting and a bridge too far. Weapon manufacturers saw the writing on the wall and little further substantive caseless development was undertaken by private industry or the government.

But HK?s G-11 did prove caseless assault rifle feasibility. Why then can?t a company like HK design an assault weapon that fires caseless ammunition today? Or, at the very least, design a modification for existing assault rifles so they can fire caseless ammunition? The answer is – they probably could. Sounds simple, right?

Maybe we need to better understand the problem.
Military assault weapons are designed to fire rapidly. Most assault rifles have a selector that can switch the weapon from semi-automatic to the automatic mode of fire with the flip of the thumb. Those who have fired even semi-automatic weapons know how rapidly they get hot. On full automatic fire, they get hot faster. A gun on automatic fire can heat up to the point where the chamber becomes so hot that the ammunition ?cooks off?, causing the weapon to ?runaway,? dangerously firing on its own without the operator pulling its trigger. This is especially true for closed bolt assault rifle operating systems. It is also the reason most machineguns have open bolt operating systems – to prevent cook offs in a hot gun. In open bolt systems a round is not chambered until the operator pulls the trigger. This releases the open bolt which subsequently closes carrying a live round forward into the chamber and the gun continues to fire until the gunner releases the trigger which catches the bolt, stopping it again in the open position.

In traditional weapons that fire metallic-case (brass-case or steel-case) ammunition, approximately 60% of the heat of combustion is removed as the casing is extracted from the chamber and ejected from the weapon. A small percentage of the remaining heat is discharged from the gun in the form of hot gases that leave the muzzle and breech as the bolt travels rearward and cycles a firing stroke. The remaining 40% of the heat ?sinks? into the weapon?s chamber, barrel extension, barrel, operating system, upper and lower receivers, and that?s why the weapon gets hot. The faster the weapon fires the hotter it gets because the heat generated from combustion simply doesn?t have time to dissipate into the surrounding air and the heat of combustion builds exponentially.

Moreover, the lighter the gun is constructed (less mass), the more rapidly it gets hot. Think of it as the time difference between heating a cup of water compared to heating a full bucket. The more mass (volume) the longer it takes to get hot. The same is true for assault rifles. The lighter they are constructed, the faster they get hot. But lighter is a sought after attribute even though it is an Achilles? Heel.

Comparing Caseless.
Now consider a weapon that fires caseless ammunition where there is no hot expended cartridge case being ejected from the weapon each time it fires. A small portion of the heat of combustion is expelled from the weapon in the form of gases, but the remainder of the heat, over 90% of it, ?sinks? into the weapon. Therefore, heat management is a major issue in caseless ammunition weapons.

Of the numerous caseless ammunition weapon designs over the past 30 years, all were plagued by the heat dissipation problem. Designs using a more conventional bolt-like mechanism and firing chamber failed miserably. Some designs explored utilizing ceramic chamber liners to reduce heat absorption; even Stellite-lined barrels have been considered. Others explored fluid jackets that act like an engine radiators to moderate heat. One design employed miniature rocket-like cartridges that didn?t require a closed breech. While caseless ammunition exposure to flame, moisture and impact were somewhat resolved, ignition reliability issues persisted and none truly solved the heat dissipation problem without penalty of massively heavy or complicated designs.

Many questions remain.
Can a caseless weapon be designed that provides distinctly superior performance above conventional assault weapons or machineguns? Can it be manufactured from conventional materials using non-exotic processes so it has comparable affordability with the guns it?s replacing? Will its performance be about the same or markedly superior to existing state-of-the art assault rifles in use today? And if it can be done, what would such a weapon mean with regard to soldier training, field and depot-level maintenance, and overall gun life expectancy? If caseless gun performance isn?t game changing, it won?t happen. This sets the bar exceedingly high for uniquely designed caseless weapons but not unachievable with today?s material and manufacturing technology. Even so, there is currently no requirement to replace the military?s in-service assault rifle with a caseless version.

But how about using polymer-case ammunition in existing assault rifles? Polymer-case ammunition is lighter than metallic-case ammunition and most existing weapons can fire it ? well, sort of. As previously discussed, heat accumulation is the root cause of most weapons? unreliability, not to mention the accelerated wear and tear on barrels and operating systems heat imposes. Lubricants break down under intense and prolonged heat. Metal parts swell, warp and change dimension. Heat is also a major safety concern, especially in light of potential ammunition ?cooks offs.? Adequate heat dissipation is perhaps the single greatest show stopper preventing the use of polymer-case ammunition as a replacement for metallic-case ammunition in conventional weapons.

Polymer-case ammunition doesn?t absorb the heat of combustion and carry it from the gun when the expended cartridge case is ejected like metallic-case ammunition does. Several polymer-case designs have attempted to mimic metallic qualities using exotic polymer formulas. To date none perform even close to their metallic-case cousins. In addition to not carrying heat, polymer-case cartridges have other problems like splitting in the chamber when fired and a soft base rim that an extractor chews to pieces, compromising reliability. Some of these problems have been solved. For example, there is one polymer-case that uses a brass base to increase extraction reliability, but the seaming of polymer and brass has its own problems and can separate leaving the polymer part of the expended cartridge in the chamber.

Manufacturing costs for polymer-case cartridges with comparable performance to metallic-case cartridges is pricey and requires more exotic processes than conventional milspec ammunition. Saving 30% or 40% in overall ammunition weight is insignificant when compared to the overall cost of the ammunition. For now, DoD logic surely follows; it is more cost effective to recruit stronger soldiers than worry about lightening the soldier?s load a few ounces and sacrifice combat-necessary reliability in the process.

The future.
Even though we are constantly bombarded by reality TV shows touting the latest greatest new weapons for battlefield use, it is unlikely that we will see the mainstream acceptance of either caseless or polymer-case ammunition any time soon – if ever. Keeping in mind the numerous environments in which wars are fought, can we ever envision a complete replacement of conventional assault rifles that fire conventional ammunition with something far more exotic? It is more likely that man-portable directed energy weapons will trump caseless kinetic weapons. A future article will discuss man-portable directed energy weapons.

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Paul Evancoe is a novelist and freelance writer. His action novels ?Own the Night,? ?Violent Peace? and ?Poison Promise? deal with terrorism and weapons of mass destruction and are available at AmazonBooks.com