Editing M109 howitzer (section)

=== K55A1 ===
[[File:2013.1.2 육군 1군단 K-55A1 포병사격 Rep.of Korea Army K-55A1 (8340099583).jpg|thumb|K55A1 howitzers firing on an exercise in 2013]]
The K55A1 is a South Korean overhaul and modernization of the K55, augmenting the proven systems of the [[K9 Thunder]] and the K9A1. The development took three years between 2007 and 2010. The upgrade started in 2010.<ref name="K55 interview"/> In November 2010, in the wake of the [[Bombardment of Yeonpyeong|North Korean artillery attack]], the South Korean government authorized a massive increase in military spending. South Korea allocated 11.5 billion KRW on K55A1 upgrades for FY2011, more than a 1500% increase from 700 million KRW for FY2010.<ref>{{Cite web |last=김 |first=남권 |title=국방위, 내년 국방예산 7천146억원 증액 의결 |url=https://n.news.naver.com/mnews/article/001/0004795198?sid=100 |access-date=2022-08-12 |website=[[Naver News]] |language=ko}}</ref> The upgrade was performed by Samsung Techwin, and the first vehicle was fielded by the South Korean Army in early 2011.<ref>{{Cite web  |title=K55A1 자주포 |url=https://kookbang.dema.mil.kr/newsWeb/m/20181211/1/BBSMSTR_000000100036/view.do |access-date=2022-08-10 |website=국방일보 |archive-date=7 April 2023 |archive-url=https://web.archive.org/web/20230407115918/https://kookbang.dema.mil.kr/newsWeb/20181211/1/BBSMSTR_000000100036/view.do |language= ko |url-status=live }}</ref>

The K55A1 is fitted with the same electronics and fire control system as the K9. The self-propelled gun has significantly enhanced field operability and accuracy through the installation of [[Honeywell Aerospace]]'s TALIN 5000 INS (inertial navigation system), a satellite navigation device (GPS), and a speed calibrator. As a result, the vehicle automatically lays the gun in the desired direction and delivers a first round within 45 seconds between stops, or 75 seconds between maneuvers after receiving the shooting specification, which required 2 minutes and 11 minutes, respectively, on the K55.<ref name="K55 interview"/><ref name="K55A1">{{Cite web  |title=생존·기동·효율성 완벽 호흡…'환상의 짝꿍' 자랑 |url=https://kookbang.dema.mil.kr/newsWeb/m/20210803/1/BBSMSTR_000000100115/view.do |access-date=2022-08-14 |website=국방일보 |archive-date=7 April 2023 |archive-url=https://web.archive.org/web/20230407115922/https://kookbang.dema.mil.kr/newsWeb/20210803/1/BBSMSTR_000000100115/view.do |language = ko |url-status=live }}</ref><ref name="youtube_MITm4IWHwpo">{{Citation |title=똑똑하게 다시 태어났다 K55A1 자주포 | date=20 January 2021 |url=https://www.youtube.com/watch?v=MITm4IWHwpo |language=en |access-date=2022-08-12}}</ref>

With the help of a new semi-autoloader, while charges are still inserted manually, the howitzer can fire 4 rounds per minute, increased from 2 to 3 rounds per minute. The improved suspension, involving a strut-type hydropneumatic buffer from Mottrol Co, Ltd., along with an enhanced chamber, allowed the vehicle to shoot K307 and K310 ammunition designed for K9 platform without laying spades at a maximum distance of 32&nbsp;km. An APU (auxiliary power unit) was installed to operate the howitzer without turning on the main engine.<ref name="K55 interview"/><ref name="K55A1"/><ref name="youtube_MITm4IWHwpo"/>

The Army Consolidated Maintenance Depot joined the K55A1 upgrade, releasing its first results in December 2013.<ref>{{Cite web  |title=전투장비 100% 성능발휘 보장 |url=https://kookbang.dema.mil.kr/newsWeb/m/20131224/2/BBSMSTR_000000010023/view.do |access-date=2022-08-10 |website=국방일보 |archive-date=7 April 2023 |archive-url=https://web.archive.org/web/20230407115918/https://kookbang.dema.mil.kr/newsWeb/20131224/2/BBSMSTR_000000010023/view.do| language= ko|url-status=live }}</ref> The upgrade cost 20% of the K9 Thunder, 800 million KRW, as of 2021.<ref name="K55A1"/> The K55A1 upgrade program was completed in December 2022.<ref>{{Citation |title=K-9만큼 똑똑해진 K55A1 업그레이드! (feat. K56) 리얼웨폰172 | date=3 January 2023 |url=https://www.youtube.com/watch?v=INi6I8Jx99o |access-date=2023-05-28 |language=ko}}</ref>