Editing M109 howitzer (section)

=== Experimental vehicles ===
==== P-52 ====
The P-52 was a 52-caliber variant of M109A6 Paladin offered to South Korea by BMY Combat Systems in 1992. It was rejected by South Korea in favor of K9 Thunder. Proposal stage only.<ref name="K9 Developer Interview (2)">{{cite AV media |date=2015-10-15 |title=[첨단국가의 초석, 방위산업] 자주포의 새 차원을 열다 – K-9 천둥(2부) |language=ko |url=https://www.youtube.com/watch?v=Lh_CVAm3XNo  |archive-url=https://ghostarchive.org/varchive/youtube/20211222/Lh_CVAm3XNo |archive-date= 2021-12-22 |url-status=live|publisher=국방TV}}{{cbignore}}</ref><ref>{{Cite web  |title=[K9 14회] "우리 자주포 우리가 개발한다"며 미측 제안 거부 |url= https://kookbang.dema.mil.kr/newsWeb/20220418/2/BBSMSTR_000000100185/view.do |access-date=2022-06-05 |website=국방일보 |archive-date=4 April 2023 |archive-url= https://web.archive.org/web/20230404151106/https://kookbang.dema.mil.kr/newsWeb/20220418/2/BBSMSTR_000000100185/view.do |url-status=dead }}</ref>

==== M109L52 ====
Jointly developed by the Dutch firm RDM and the German firm [[Rheinmetall]], the M109L52 was first revealed in 2002. The main improvement was replacing the M126 series gun with the longer 52-caliber cannon from the [[PzH 2000]], thus the MTLS ammunition of the PzH 2000 can be used. Improvements to the loading system were also made, resulting in an increased rate of fire from 3 rds/min to 9–10 rds/min, able to be sustained for up to 2 minutes. A total of 35 rounds can be carried.

==== M109-52 ====
The M109-52 is a 52-caliber variant of M109 developed by BAE Systems by integrating Rheinmetall L52 cannon.<ref>{{Cite web |url=https://www.baesystems.com/en-us/product/m109-52-self-propelled-howitzer |title=M109-52 self-propelled howitzer |publisher=BAE Systems |access-date=2023-12-01}}</ref>

==== M1299 ====
{{Main|M1299 howitzer}}
The M1299 was a prototype [[self-propelled howitzer]] developed by BAE Systems in 2019 under the '''Extended Range Cannon Artillery''' (ERCA) program. It was based on the M109A7, and was primarily designed for the purpose of improving the M109A7's effective range.  One battalion of vehicles is planned to begin a year-long operational assessment in 2023. It was expected to be fitted with an [[autoloader]], which would have increased its rate of fire from 3 to 10 rounds per minute.<ref>{{cite web | url=https://breakingdefense.com/2020/03/new-army-cannon-doubles-range/ | title=New Army Cannon Doubles Range; Ramjet Ammo May be Next | date=6 March 2020 }}</ref><ref>[https://breakingdefense.com/2021/03/army-outlines-ambitious-schedule-for-robots-armor/ Army Outlines Ambitious Schedule For Robots, Armor]. ''Breaking Defense''. 19 March 2021.</ref> The M1299 was cancelled in March 2024 due, at least in part, to excessive barrel wear. Advanced ammunition developed for the M1299 will continue development, and the U.S. Army will look for existing alternatives to fulfil its re-evaluated long-range fire support needs.<ref>{{Cite web |last=Judson |first=Jen |date=2024-03-11 |title=US Army scraps Extended Range Cannon Artillery prototype effort |url=https://www.defensenews.com/land/2024/03/11/us-army-scraps-extended-range-cannon-artillery-prototype-effort/ |access-date=2024-03-22 |website=Defense News |language=en}}</ref>