View source for Engineering:Caseless ammunition

{{Short description|Type of weapon-cartridge}}
{{Multiple image
|total_width = 300
|header = {{big|Caseless ammunition}}
|image1 = Gerasimenko ctgs variants (cropped 2).jpeg
|caption1 = {{center|Internal propellant}} Caseless ''7.62 mm Gerasimenko'' projectile with internal propellant. Used in the {{nowrap|{{ill|VAG-73|ru|ВАГ-73}}}} [[Engineering:Machine pistol|machine pistol]].
|image2 = 473and223.png
|caption2 = {{center|External propellant}} Comparison of .223 Remington (left) and external propellant caseless 4.73×33mm Heckler & Koch G11 ammunition (right).
}}
'''Caseless ammunition''' ('''CL'''),<ref name="quarryhs 40 mm CL">{{cite web |author1=Anthony G Williams |author2=Emmanuel Gustin |author3=Henning Ruch (acknowledgements) |title=WORLD WAR 2 FIGHTER ARMAMENT EFFECTIVENESS, tables 1-2, 4 |url=https://www.quarryhs.co.uk/WW2guneffect.htm |website=quarryhs.co.uk |access-date=2022-07-02 |quote=40mm CL}}</ref> or '''caseless cartridge''', is a configuration of [[Engineering:Cartridge (firearms)|weapon-cartridge]] that eliminates the cartridge case that typically holds the [[Engineering:Percussion cap|primer]], [[Physics:Propellant|propellant]] and [[Physics:Projectile|projectile]] together as a unit. Instead, the propellant and primer are fitted to the projectile in another way so that a cartridge case is not needed, for example inside or outside the projectile depending on configuration.

Caseless ammunition is an attempt to reduce the weight and cost of ammunition by dispensing with the case, which is typically precision made of [[Chemistry:Brass|brass]] or steel, as well as to simplify the operation of repeating guns by eliminating the need to extract and eject the empty case after firing.<ref name="explosives">{{cite book |title=Explosives |url=https://archive.org/details/Explosives._6th_Edition |last1=Meyer |first1=Rudolf |last2=Köhler |first2=Josef |last3=Homburg |first3=Axel |publisher= Wiley-VCH |date=2007| isbn=978-3-527-31656-4}}</ref> Its acceptance has been hampered by problems with production expenses, heat sensitivity, sealing, and fragility. Its use to date has been mainly limited to prototypes and low-powered guns, with some exceptions.

== Internal propellant caseless ammunition ==
=== Description ===
[[File:40 mm Ho-301 shell.png|thumb|Cross section of internal propellant caseless ammunition, type {{nowrap|''[[Engineering:Ho-301 cannon|40 mm Ho-301]]''}}.<ref name="quarryhs Ho-301">{{cite web |author1=Anthony G Williams |author2=Emmanuel Gustin |author3=Henning Ruch (acknowledgements) |title=WORLD WAR 2 FIGHTER ARMAMENT EFFECTIVENESS: Comments on Table 3 |url=https://www.quarryhs.co.uk/WW2guneffect.htm |website=quarryhs.co.uk |access-date=2022-07-02 |quote=The Japanese made an interesting attempt to improve the firepower of the Ki-44 by installing the 40 mm Ho-301 cannon, firing caseless ammunition. But the 245 m/s muzzle velocity of these weapons was far too low, and they failed in combat. Not many of these Ki-44-IIc aircraft were built.}}</ref>]]
[[File:Gerasimenko 2ctgs and primer 1 (cropped).jpeg|thumb|''7.62 mm Gerasimenko'', internal propellant caseless ammunition used in the {{nowrap|{{ill|VAG-73|ru|ВАГ-73}}}} machine pistol]]
Older caseless ammunition typically uses a configuration where the primer and propellant get integrated into the bottom of the projectile, much like a rocket. When fired, the propellant gas is vented out the back of the projectile to accelerate it to speed. Unlike rocket projectiles, which have similar configurations, the propellant of "internal propellant caseless ammunition" has an instant burn time like a traditional cartridge (under 0.2 seconds),<ref name="Raketbeväpning">{{Cite book|last=Sjögren|first=Sven|title=Raketbeväpning i svenska flygvapnet, FV raketbeväpning 1944-1954|publisher=Kungliga Flygförvaltningen (Royal Swedish Air Force Materiel Administration)|location=Stockholm, Sweden|page=6|trans-title=Rocket-armament in the Swedish air force, AF rocket-armament 1944-1954|language=sv}}</ref> meaning the propellant burns up before the projectile leaves the barrel, preferrably inside the [[Engineering:Chamber (firearms)|chamber]]. Rocket projectiles, in comparison, have propellant burn times of over 0.2 seconds, usually several seconds, meaning rocket propellant traditionally propels the rocket for a certain distance from the launcher.<ref name="Raketbeväpning"/>

Another difference is means of fire and stabilization. As a cartridge, internal propellant caseless ammunition is only fired from [[Engineering:Gun barrel|gun barrel]]s, either closed or recoilless, and achieves [[Physics:Ballistics|ballistic]] stabilization through longitudinal spinning (conservation of angular momentum), either by the use of [[Engineering:Driving band|driving band]]s and [[Engineering:Rifling|rifling]] or oblique [[Physics:Nozzle|nozzle]]s for the propellant gas.<ref name="Raketbeväpning"/> Rockets, in contrast, can be fired from more platforms than gun barrels, for example, rails, and traditionally use fins for stabilization, either fixed or foldable.<ref name="Raketbeväpning"/>

=== History ===
An early type of internal propellant caseless ammunition was Walter Hunt's Rocket Ball cartridge. It was developed in the 1850s and the guns using it were sold primarily by Volcanic Repeating Arms. Hunt's Rocket Ball cartridges were severely under-powered and never saw wide acceptance for self-protection, hunting, or military use.<ref>{{cite web|url=https://winchestercollector.org/?s=volcanic|title=volcanic - Search Results - Winchester Collector|website=winchestercollector.org}}</ref>

During [[Social:World War II|World War II]], Germany began an intensive program to research and develop a practical internal propellant caseless ammunition cartridge for military use, which was driven by the rising scarcity of metals, especially copper used to make cartridge cases. The Germans had some success, but not sufficient to produce a caseless cartridge system during the war.<ref name="cotw10">{{cite book |title=Cartridges of the World|edition=10th |publisher=Krause Publications |last=Barnes |first=Frank C. |year=2003 |editor1-first=Stan |editor1-last=Skinner |isbn=0-87349-605-1 |page=8}}</ref> One quasi-example which almost entered production was the 55 mm Maschinenkanone MK 155. It used partially combustible cartridges similar to the ones used in the popular [[Engineering:Rheinmetall Rh-120|Rheinmetall Rh-120]] tank gun today. Japan, however, successfully developed an aircraft mounted [[Engineering:Autocannon|autocannon]] using internal propellant caseless ammunition during the war. Named [[Engineering:Ho-301 cannon|Ho-301]], it was a 40 mm autocannon and saw limited action in the defense of the Japanese home islands during the waning months of the war.<ref name="quarryhs Ho-301"/>

After WWII the use of internal propellant caseless ammunition largely disappeared from mainstream weapons development, however the type saw a small resurgence when the [[Place:Soviet Union|Soviet Union]] introduced their [[Engineering:GP-25|GP-25]] 40 mm internal propellant caseless under-barrel grenade launcher in 1978. This was followed by the Russian-developed AGS‑40 Balkan 40 mm internal propellant caseless [[Engineering:Automatic grenade launcher|automatic grenade launcher]] in 2017.<ref>{{cite web|url=https://www.armyrecognition.com/weapons_defence_industry_military_technology_uk/new_ags-40_balkan_40mm_automatic_grenade_launcher_will_enter_in_service_with_russian_army_tass_11311161.html|title=New AGS-40 Balkan 40mm automatic grenade launcher will enter in service with Russian army TASS 11311161 - weapons defence industry military technology UK - analysis focus army defence military industry army|last=Administrator|website=www.armyrecognition.com}}</ref><ref name=Balkan1>{{cite web|url=http://lenta.ru/news/2013/02/18/balkan/|title=Lenta.ru: Оружие: Вооружение: Россия вооружится новым крупнокалиберным гранатометом|publisher=Lenta.ru |language=ru|access-date=21 October 2014}}</ref>

=== Issues ===
Since propellant is blasted out the back of the projectile during fire, many historical guns using internal propellant caseless ammunition have had problems with residue buildup from the propellant, leading to malfunctions. To decrease residue buildup, historical systems have often been forced to use lower amounts of propellant in the ammunition or adopting a recoilless solution for the gun where some of the burning propellant is vented out the back of the gun when firing.<ref name="Raketbeväpning"/> This, however, causes problems on its own as less propellant is being used to propel the ammunition, leading to less potent [[Physics:Muzzle velocity|muzzle velocities]], often under the [[Physics:Speed of sound|speed of sound]] (~{{convert|200-250|m/s|ft/s|abbr=on}}).<ref name="Raketbeväpning"/><ref name="quarryhs Ho-301"/> This is equal to the muzzle-velocities of many mortar-weapons which are meant to be fired at high angles of elevation with heavy projectile arcs. Caseless ammunition weapons are often meant for horizontal fire, meaning that highly sub-sonic ammunition leads to very limited range and poor accuracy due to the rapid loss of projectile velocity.<ref name="Raketbeväpning"/><ref name="quarryhs Ho-301"/>

=== Gallery ===
<gallery widths="150" heights="150">
File:Rocket-Ball (cropped).JPG|Volcanic .41 Rocket Ball internal propellant caseless ammunition cartridge
File:J 21R IP.png|Proposed CL-armament for the [[Engineering:Saab 21R|Saab 21R]], consisting of four 95 mm internal propellant caseless cannons mounted in the wings
File:Gerasimenko 2ctgs and primer 1.jpeg|7.62 mm Gerasimenko internal propellant caseless ammunition for the {{nowrap|{{ill|VAG-73|ru|ВАГ-73}}}} [[Engineering:Machine pistol|machine pistol]]
File:VOG-25 7P17 - MAKS2015part7-50 (cropped).jpg|VOG-25 7P17 internal propellant caseless ammunition for the 40 mm [[Engineering:GP-25|GP-25]] under-barrel grenade launcher
File:AGS-40 grenade launcher - Oboronexpo2014part4-46 (cropped 2).jpg|7P39 internal propellant caseless ammunition for the 40 mm AGS‑40 Balkan [[Engineering:Automatic grenade launcher|automatic grenade launcher]]
</gallery>

== External propellant caseless ammunition ==
=== Description ===
[[File:Heckler & Koch ACR Caseless Cartridge.png|thumb|Cross section of external propellant caseless ammunition, type ''{{nowrap|4.92 × 34{{nbsp}}mm}} Heckler & Koch'']]
[[File:4.73x33 Caseless-crop.jpg|thumb|''4.73 × 33 mm Heckler & Koch'', external propellant caseless ammunition disassembled. The components are, from left to right: the solid propellant, the primer, the bullet, and a plastic cap that serves to keep the bullet centered in the propellant block.]]
Modern caseless ammunition typically uses a configuration in which the primer and projectile gets integrated into a solid mass of external propellant (originally [[Chemistry:Nitrocellulose|nitrocellulose]]), cast to form the body of the cartridge. Cavities exist in the body to accept the bullet and a primer (both of which are glued into place). The completed cartridge might also contain a booster charge of powdered propellant to help ignite the body and provide initial thrust to the bullet.<ref name="explosives"/> Many of these external propellant caseless cartridges are also telescoped, with the bulk of the bullet held within the body of the cartridge, to cut down on cartridge length. A shorter cartridge cuts down on the distance the firearm's action must reciprocate to load a new round, which allows for higher cyclic rates and greater probability of multiple hits on a target at long range. Lack of a case also reduces the weight of the cartridge substantially, especially in small bore rifles. For example, the external propellant caseless ammunition designed by Austrian inventor Hubert Usel (1926–2010) for the [[Engineering:Voere VEC-91|Voere VEC-91]] weighs about one third as much as regular ammunition for the same caliber.<ref name="voere">{{cite web|url=http://www.voere.com/firearms.htm |archive-url=https://web.archive.org/web/20080613193217/http://www.voere.com/firearms.htm |archive-date=2008-06-13 |title=Voere |url-status=dead }}</ref><ref name="brassey">{{cite book |title=Brassey's Encyclopedia of Land Forces and Warfare |last=Margiotta |first=Franklin D. |publisher=Brassey's |date=1997 |isbn=9781574880878}}</ref><ref name="wounds">{{cite book |title=Gunshot Wounds |last=DiMaio |first=Vincent J.M. |publisher=CRC Press |date=1998 |isbn=978-0-8493-8163-8 |url-access=registration |url=https://archive.org/details/gunshotwoundspra00dima }}</ref>

=== Issues ===
While it seems a simple operation to replace the case with a piece of solid propellant, the cartridge case provides more than just a way to keep the cartridge components together, and these other functions must be replaced if the case is to be replaced. External propellant caseless ammunition is not without its drawbacks, and it is these drawbacks that have kept modern external propellant caseless ammunition from achieving wider success.

==== Heat sensitivity ====
The first major problem, of special concern in military applications, which often involve sustained firing, is the heat sensitivity of the ammunition. Nitrocellulose, the primary component of modern firearm [[Chemistry:Smokeless powder|propellant]], ignites at a relatively low temperature of around 170&nbsp;°C (338&nbsp;°F). One of the functions of the metallic cartridge case is as a [[Physics:Heat sink|heat sink]]; when extracted after firing, every metallic case carries away a significant amount of the heat from the combustion of the propellant, slowing the rate at which heat builds up in the chamber. The thermal insulation provided by the case also works the other way around, shielding the propellant from built-up heat in the chamber walls.

Without a case to provide these functions, external propellant caseless rounds using nitrocellulose will begin to cook off, firing from the residual chamber heat, much sooner than cased cartridges do. Cooking off can be avoided by designing the weapon to [[Engineering:Open bolt|fire from an open bolt]], but this introduces other problems, and thus is only suitable for smaller calibre [[Engineering:Machine gun|machine gun]]s and [[Engineering:Submachine gun|submachine gun]]s.

The normal solution to the problem of heat is to increase the heat resistance by switching to a propellant with a higher ignition temperature, typically a non-crystalline explosive carefully formulated to provide an appropriate rate of combustion.<ref name="explosives" /><ref name="brassey"/> Heckler & Koch, in concert with Dynamit Nobel, managed such a task by producing relatively heat-resistant external propellant caseless ammunition.

==== Sealing ====
Another important function provided by the cartridge is to seal the rear of the chamber. During firing of a cased cartridge, the pressure in the chamber expands the metallic case, which [[Engineering:Obturation|obturates]] to the chamber. This prevents gas exiting from the rear of the chamber, and it has also been experimentally shown to provide a significant amount of support to the bolt. Without the case to provide this seal, the firearm design must account for this and provide a means of sealing the rear of the chamber. This problem was also encountered with the Dreyse needle gun; the French Chassepot solved the leaking-breech problem with the addition of a rubber seal to the bolt.<ref>{{cite book |title=Handbook for Shooters & Reloaders |volume=I |last=Ackley |first=P.O.|publisher=Plaza Publishing |date=1962 |isbn=978-99929-4-881-1}}</ref><ref>See main article, Chassepot, for references</ref>

Telescoped external propellant caseless rounds must also deal with the issue of blocking the bore, as the bullet is surrounded by propellant. The booster charge is used to address this issue, providing an initial burst of pressure to force the bullet out of the cartridge body and into the barrel before the body combusts.<ref name="wounds"/>

==== Fragility ====
External propellant caseless rounds are limited by the fact that the cartridge body is primarily a propellant, and structural properties are secondary to the combustion properties. The primary issue is one of extraction. While caseless ammunition eliminates the need to extract a fired case, unfired caseless rounds must be extractable to unload the firearm or to clear a misfire. With metallic cases, this ability is provided by a rim or extractor groove machined into the rear of the case. Even in completely plastic-bodied cartridges, such as the Activ brand shotgun shells, a thin metal ring is molded into the rim to provide support for the extractor.<ref name="cotw10"/><ref name="brassey"/><ref name="wounds"/> A secondary issue is that ammunition in use can be exposed to air, water, lubricants, and solvents. Primer and propellant in external propellant caseless rounds is unprotected, while cartridge cases provide a high degree of protection.

=== External propellant caseless guns ===
One of the first caseless firearm and ammunition systems produced was made by Daisy, the airgun maker, in 1968. The Daisy V/L rifle uses a .22 caliber (5.5&nbsp;mm) low-powered external propellant caseless round with no primer. The rifle was basically a spring-piston air rifle, but when used with the V/L ammunition the energy from the compression of the piston heated the air behind the caseless cartridge enough to ignite the propellant, and this generated the bulk of the energy of firing. The Daisy V/L rifle system was discontinued in 1969 after the ATF ruled that it was not an airgun, but a firearm, which Daisy was not licensed to produce.<ref>{{cite book |title=Blue Book of Gun Values|edition=13th |last=Fjestad |first=S. P. |publisher=Blue Book Publications}}</ref>

Some [[Engineering:Assault rifle|assault rifle]]s have used external propellant caseless ammunition. One of the better-known weapons of this type is the G11 made by Heckler & Koch as a potential replacement for the G3 battle rifle. Although the G11 never entered full production, it went through a number of prototype stages as well as field testing, including testing as part of the American [[Engineering:Advanced Combat Rifle|Advanced Combat Rifle]] program. While it was scheduled to be adopted by the West German military with a plan set out to procure 300,000 G11K2 rifles over a period from 1990 to 2002, the expenses created by the reunification of Germany and the impossibility of modifying the G11 to use NATO-standard ammunition led to the cancellation of the G11 project and the adoption of a cheaper, more conventional NATO-standardised assault rifle, the 5.56{{nbsp}}mm G36. The G11's caseless ammunition was later used as the basis for the caseless round development in the US [[Engineering:Lightweight Small Arms Technologies|Lightweight Small Arms Technologies]] program.

The first commercial external propellant caseless rifle featuring [[Engineering:Electronic firing|electronic firing]] was the [[Engineering:Voere VEC-91|Voere VEC-91]].<ref name="voere"/>

== See also ==
* {{annotated link|Engineering:Blunderbuss}}
* {{annotated link|Engineering:Coilgun}}
* {{annotated link|Engineering:Gyrojet}}

== References ==
{{reflist}}
* Starry, Donn A., General. ''Mounted Combat in Vietnam.'' Department of the Army, Washington D.C., 1978.

== External links ==
* [https://web.archive.org/web/20080723122951/http://www.65grendel.com/art002arammo.htm Assault Rifle Ammunition History]
* [https://patents.google.com/patent/US8342097B1/en]

{{emerging technologies|topics=yes|military=yes}}

{{DEFAULTSORT:Caseless Ammunition}}
[[Category:Caseless firearms]]
[[Category:Military technology]]

{{Sourceattribution|Caseless ammunition}}