Editing M109 howitzer (section)

=== M109A1 ===
[[File:United States Army M109A1 self-propelled howitzer in Germany during exercise REFORGER '82.jpg|thumb|US Army M109A1 in 1982|left]]
Fielded in 1973, this modification replaced the M126 cannon with a 39 caliber M185, featuring a longer barrel while increasing maximum range to 18,100 meters.<ref name=":0">{{Cite journal |date=October 1989 |title=Numbering the M109 Howitzers |url=https://books.google.com/books?id=Hgh5tz5WsQoC&pg=PA52 |journal=Field Artillery |publisher=US Field Artillery Association |pages=52 |issn=0899-2525}}</ref>

==== M109A1B ====
The M109 rebuilt to M109A1 standard.

==== M109 66/74 ====
{{Main|M109 in the Swiss Armed Forces}}
The M109 (Pz Hb) 66/74 is a Swiss upgraded M109 (Pz Hb 66) to M109A1B (Pz Hb 74) standard.

Switzerland purchased 146 M109 under the armament program 1968, and introduction of the howitzer started in 1971.<ref name="Pz Hb 66">{{Cite web |title= Panzerhaubitze 66 M-109 / L-2315,5 cm Pz Hb 66 - Panzerhaubitzen - Raupenfahrzeuge {{!}} militärfahrzeuge.ch |url=https://militaerfahrzeuge.ch/unterkategorie_13_31_355.html |access-date=2023-07-28 |website=militaerfahrzeuge.ch}}</ref> All vehicles received upgrade to M109A1B (Pz Hb 74) standard and were delivered from May 1977 to February 1979.<ref name="Pz Hb 66/74">{{Cite web |title=Panzerhaubitze 66/74 M-109 / L-39Pz Hb 66/74 - Panzerhaubitzen - Raupenfahrzeuge  |url=https://militaerfahrzeuge.ch/unterkategorie_13_31_475.html |access-date=2023-07-28 |website= Militaerfahrzeuge}}</ref>