Editing SA80 (section)

===1960s – 1970s: 4.85×49mm, XL64, XL65, XL68===
{{further|L64/65|intermediate cartridge}}
In 1969, the Enfield factory began work on a brand new family of weapons, chambered in a newly designed British [[4.85×49mm]] intermediate cartridge. While the experimental weapon family was very different from the EM-2 in internal design and construction methods, its bullpup configuration with an optical sight was a clear influence on the design of what was to become the SA80. The system was to be composed of two weapons: the [[L64/65|XL64E5]] rifle (also called the "Enfield Individual Weapon") and a light support weapon known as the XL65E4 [[light machine gun]].

The sheet metal construction and the design of the bolt, bolt carrier, guide rods and the weapon's disassembly showed strong similarities to the [[ArmaLite|Armalite]] [[AR-18]] which was manufactured under licence from 1975 to 1983 by the [[Sterling Armaments Company]] of [[Dagenham]], [[Essex]],<ref name="OffTarget">{{citation |title=Off Target |first=James |last=Meek |newspaper=The Guardian |date=10 October 2002 |url=https://www.theguardian.com/uk/2002/oct/10/military.jamesmeek}}</ref><ref>{{citation |title=Military Small Arms of the 20th Century |edition=4th |first1=Ian V. |last1=Hogg |first2=John |last2=Weeks |isbn=978-0-910676-28-1 |year=1981|publisher=DBI Books }}</ref>{{page needed|date=July 2021}} and which had been tested by the [[Ministry of Defence (United Kingdom)|British Ministry of Defence]] in 1966 and 1969.<ref>{{citation |title=A Historical Review of Armalite |date=4 January 2010 |publisher=ArmaLite Inc. |url=http://www.armalite.com/images/Library\History.pdf |archive-url=https://web.archive.org/web/20140612010558/http://www.armalite.com/images/Library/History.pdf |archive-date=2014-06-12}}</ref>

During the development of the SA80, a bullpup conversion was made of an AR-18 and a [[Stoner 63]]<ref>{{citation |title=The World's Assault Rifles |first1=Gary Paul |last1=Johnston |first2=Thomas B. |last2=Nelson |chapter=Chapter 29 Great Britain}}</ref>{{page needed|date=April 2022}}<ref>{{cite web|url=https://www.forgottenweapons.com/sa80-history-the-first-mockups-sterling-and-stoner/|title=SA80 History: The First Mockups (Sterling and Stoner) |date=5 May 2017|website=[[Forgotten Weapons]]|access-date=30 May 2017}}</ref> at Enfield due to the fact they could be used with stocks folded/without stocks which allowed the bullpup conversion and were later chambered in the experimental 4.85x49mm round. A bullpup conversion of the [[AR-15 style rifle|AR-15]] was previously considered but the buffer tube in stock prevented the idea from reaching fruition.<ref>The World's Assault Rifles by Gary Paul Johnston, Thomas B. Nelson, Chapter 67</ref>

Technically, in the mid-1970s, the 4.85×49mm round was seen as superior to the then existing version of 5.56mm M193 round in use by the US (for the [[M16 rifle|M16/M16A1]]) and by other forces. This was the expressed view of trials team members whilst demonstrating the XL64E5 prototype at the British Army School of Infantry at [[Warminster]]. Development of small-arms munitions have a long and continuous life and it was estimated by the trials specialists from Enfield that this weapon would ultimately be superior in the 4.85mm configuration. For the 4.85mm round, both propellant and projectile were at the beginning of their respective development curves. Weight for weight, more rounds of ammunition could be carried by an individual soldier – a considerable advantage on the battlefield.

It was regarded as probable at the time that the argument for the 5.56mm standard within NATO had more to do with the economics involved. Over the lifetime of a small-arms weapon type, far more money is spent on the munitions than the weapons themselves. If the 5.56mm supporters had lost the argument in favour of a British 4.85mm round, the economic impact would have been very large, and political pressure undoubtedly played a part in the final decision.{{citation needed|date=July 2021}} In 1976, the prototypes were ready to undergo trials.{{citation needed|date=July 2021}}