Editing M109 howitzer (section)

=== M109A2 ===
Incorporated 27 [[Reliability, availability, maintainability and safety|Reliability, Availability, and Maintainability (RAM)]] mid-life improvements. Most notably, the long barreled 155&nbsp;mm M185 Cannon in the new M178 gun mount, ballistic protection for the panoramic telescope, counterbalanced travel lock, and the ability to mount the M140 bore sight alignment device. Stowage of 155 mm rounds increased from 28 to 36 rounds; .50cal ammunition remained at 500 rounds. Fielded in 1979.<ref name=":0" />

During M109A2 production, a slightly simplified version was also produced for export. This had minor internal changes and deleted the hull flotation feature. These were designated '''M109A1B'''.<ref>{{cite book |last1=Lathrop|first1=R.|title=M109 155mm Self-Propelled Howitzer 1960–2005|date=5 Feb 2005|publisher=Osprey |isbn=978-1-84176631-7|page=15}}</ref>

==== K55 ====
[[File:2013.3. 해병대 자주포 기동훈련 Rep.of Korea Marine Corps Self-propelled artillery Maneuvers (8553361055).jpg|left|thumb|K-55 howitzers of [[Republic of Korea Marine Corps]] in 2013]]
The K55 is a South Korean license produced variant of the M109A2. In the 1960s, the [[Republic of Korea Army|South Korean Army]] received [[M107 self-propelled gun|M107]] and [[M110 howitzer|M110]] from the United States. However, the number of these self-propelled guns was insufficient to counter rapidly-growing North Korean artillery capabilities. In the 1970s, South Korea began mass-producing towed howitzers locally, but intelligence reports of North Korean [[M-1978 Koksan|170 mm self-propelled artillery]] forced South Korea to look for a new self-propelled artillery system.<ref name="K55 interview" />

In December 1983, the ministers of defense of the United States and South Korea signed a [[memorandum of understanding]] (MOU) to co-produce M109A2 in South Korea using American technical data. The United States delivered two completed M109A2s to South Korea for operational review, and the [[Agency for Defense Development]] began to translate the data package and created field and maintenance manuals for soldiers. South Korea wanted to produce every part of the vehicle domestically; however, due to the amendment bill by Rep. [[Samuel S. Stratton]] of New York, which established a limit for foreign military technology cooperation, the turret and the M185 cannon from [[Watervliet Arsenal]] were imported from the United States.<ref name="K55 interview"/>

Compared to the M109A2, besides 63 percent of parts being produced locally, K55 has a driver's night periscope and light exposure minimization device to enhance night-time operations as well as additional radio systems. The vehicle has a [[CBRN defense|nuclear, biological and chemical]] protection system and halon fire extinguishers. A total of 1,180 K55s were produced between 1985 and 1996.<ref name="K55 interview"/><ref name="K66">{{Cite web |title=[김대영의 무기 인사이드] 우리 군에서 영구 결번된 비운의 국산장갑차 'K66' |url=https://nownews.seoul.co.kr/news/newsView.php?id=20210316601008 |access-date=2022-08-08 |website=나우뉴스 | date=16 March 2021 |language=ko}}</ref> The vehicle's name was changed from KM109A2 to K55, originally a code name from the Samsung factory.

In November 1990, the United States and South Korea signed an agreement to allow South Korea to supply M109 parts to third parties.<ref>{{Cite web |last=李敦琯|title=한반도 전쟁발발시 美전투력 즉각 증강 |url=https://n.news.naver.com/mnews/article/001/0003458242?sid=102 |access-date=2022-08-08 |website=[[Naver News]] |language=ko}}</ref> In May 1997, during the Security Cooperation Committee held in Washington D.C., South Korea requested that the United States revise the MOU to export complete K55s, originally intended for domestic use only. South Korea was expecting to export 72 K55s and four ammunition support vehicles to Brazil for $160 million over Belgium's offer, but the [[United States Department of Defense]] declined the request to avoid an arms race in the region.<ref>{{Cite web |title=국산 1백55mm 자주포 대량수출 전망 |url=https://n.news.naver.com/mnews/article/001/0004226305?sid=102 |access-date=2022-08-08 |website=[[Naver News]] |language=ko}}</ref><ref>{{Cite web |title=1백55mm 국산자주포 수출 무산 |url=https://n.news.naver.com/mnews/article/001/0004248291?sid=102 |access-date=2022-08-08 |website=[[Naver News]] |language=ko}}</ref>

In May 1998, the South Korean military began operating a K55 simulator to boost artillery operator training. The simulator took a year and a billion [[South Korean won|KRW]] budget to develop. It is expected to save 150 million KRW per year per device.<ref>{{Cite web |last=朴成雨|title=포병학교 자주포 조종 시뮬레이터 개발 |url=https://n.news.naver.com/mnews/article/001/0004367835?sid=102 |access-date=2022-08-08 |website=[[Naver News]] |language=ko}}</ref>