View source for M109A1

{{About
|about = American tank destroyer '''{{PAGENAME}}'''
|usage = other versions
|link = M109 (Family)
}}
{{Specs-Card
|code=us_m109a1
|images={{Specs-Card-Image|GarageImage_{{PAGENAME}}.jpg}}
}}

== Description ==
<!-- ''In the description, the first part should be about the history of the creation and combat usage of the vehicle, as well as its key features. In the second part, tell the reader about the ground vehicle in the game. Insert a screenshot of the vehicle, so that if the novice player does not remember the vehicle by name, he will immediately understand what kind of vehicle the article is talking about.'' -->
The '''{{Specs|name}}''' was introduced into American service in 1973 as an improved version of the M109 self-propelled howitzer. The main improvement was the installation of a new 155 mm M185 cannon, which had a longer barrel and a higher muzzle velocity than the previous M126. This increased the effective range of the M109A1 from 14.6 km to 18 km, giving it an advantage over foreign artillery. The M109A1 also had a new loading assist system that automated some of the loading procedures and reduced the workload of the crew. It was known for its role in supporting the US Army's operations in Europe and the Middle East, where it could provide fire support for ground forces and counter-battery fire against enemy artillery. The existing M109A1's were later converted to the M109A2 standard, which incorporated 27 RAM (Reliability, Availability, Maintability) improvements.

The {{Specs|name}} was introduced in [[Update "Kings of Battle"]]. It has similar characteristics to the Soviet [[2S3M]] and can deliver powerful 155 mm shells over long distances and relocate swiftly to evade enemy fire. The M109A1 has a fast rate of fire, thanks to its semi-automatic loader and large ammo capacity, and its mobility is complemented by a good top speed and acceleration. However, its armor is not very thick, so it's recommended to use the M109A1's speed to avoid direct confrontations when possible. Moreover, it is essential to keep in mind that the M109A1 has low gun depression and cannot depend on firing from elevated positions.

== General info ==
=== Survivability and armour ===
{{Specs-Tank-Armour}}
<!-- ''Describe armour protection. Note the most well protected and key weak areas. Appreciate the layout of modules as well as the number and location of crew members. Is the level of armour protection sufficient, is the placement of modules helpful for survival in combat? If necessary use a visual template to indicate the most secure and weak zones of the armour.'' -->
The armour on the M109 is nearly non-existent, being surrounded by 32 mm thick aluminium alloy 5083, which effectively comes down to 13-20 mm RHA. This leaves the vehicle vulnerable to even light machine gun fire from any angle. The weakness of the armour turns into a strong-suit against AP shells that will pass straight through, unable to fuse or create enough spall to inflict major damage. Direct hits from HE and other chemical shells will most likely leave the M109 a burning wreck. The 6 crew members are pretty spaced apart in the turret, giving a plus to crew survivability.

'''Armour type:''' <!-- The types of armour present on the vehicle and their general locations -->
<!-- Example: * Rolled homogeneous armour (Front, Side, Rear, Hull roof)
* Cast homogeneous armour (Turret, Transmission area) -->

{| class="wikitable"
|-
! Armour !! Front (Slope angle) !! Sides !! Rear !! Roof
|-
| Hull || ___ mm || ___ mm ''Top'' <br> ___ mm ''Bottom'' || ___ mm || ___ - ___ mm
|-
| Turret || ___ - ___ mm ''Turret front'' <br> ___ mm ''Gun mantlet'' || ___ - ___ mm || ___ - ___ mm || ___ - ___ mm
|-
| Cupola || ___ mm || ___ mm || ___ mm || ___ mm
|-
|}

'''Notes:''' <!-- Any additional notes which the user needs to be aware of -->
<!-- Example: * Suspension wheels are 20 mm thick, tracks are 30 mm thick, and torsion bars are 60 mm thick. -->

=== Mobility ===
{{Specs-Tank-Mobility}}
<!-- ''Write about the mobility of the ground vehicle. Estimate the specific power and manoeuvrability, as well as the maximum speed forwards and backwards.'' -->
''Write about the mobility of the ground vehicle. Estimate the specific power and manoeuvrability, as well as the maximum speed forwards and backwards.''

{{tankMobility|abMinHp=575|rbMinHp=358}}

=== Modifications and economy ===
{{Specs-Economy}}

== Armaments ==
{{Specs-Tank-Armaments}}
=== Main armament ===
{{Specs-Tank-Weapon|1}}
<!-- ''Give the reader information about the characteristics of the main gun. Assess its effectiveness in a battle based on the reloading speed, ballistics and the power of shells. Do not forget about the flexibility of the fire, that is how quickly the cannon can be aimed at the target, open fire on it and aim at another enemy. Add a link to the main article on the gun: <code><nowiki>{{main|Name of the weapon}}</nowiki></code>. Describe in general terms the ammunition available for the main gun. Give advice on how to use them and how to fill the ammunition storage.'' -->
{{main|M185 (155 mm)}}

''Give the reader information about the characteristics of the main gun. Assess its effectiveness in a battle based on the reloading speed, ballistics and the power of shells. Do not forget about the flexibility of the fire, that is how quickly the cannon can be aimed at the target, open fire on it and aim at another enemy. Add a link to the main article on the gun: <code><nowiki>{{main|Name of the weapon}}</nowiki></code>. Describe in general terms the ammunition available for the main gun. Give advice on how to use them and how to fill the ammunition storage.''

{| class="wikitable" style="text-align:center" width="100%"
|-
! colspan="5" | [[M185 (155 mm)|155 mm M185]] || colspan="5" | Turret rotation speed (°/s) || Reloading rate (seconds)
|-
! Mode !! Capacity !! Vertical !! Horizontal !! Stabilizer
! Stock !! Upgraded !! Full !! Expert !! Aced
! Autoloader
|-
! ''Arcade''
| rowspan="2" | 28 || rowspan="2" | -3°/+75° || rowspan="2" | ±180° || rowspan="2" | - || __._ || __._ || __._ || __._ || __._ || rowspan="2" | _.__
|-
! ''Realistic''
| __._ || __._ || __._ || __._ || __._
|-
|}

==== Ammunition ====
{{:M185 (155 mm)/Ammunition|M107, M107 (PF), M110}}

==== [[Ammo racks]] ====
<!-- [[File:Ammoracks_{{PAGENAME}}.png|right|thumb|x250px|[[Ammo racks]] of the {{PAGENAME}}]] -->
<!-- '''Last updated:''' -->
{| class="wikitable" style="text-align:center"
|-
! Full<br>ammo
! 1st<br>rack empty
! 2nd<br>rack empty
! 3rd<br>rack empty
! 4th<br>rack empty
! 5th<br>rack empty
! 6th<br>rack empty
! Visual<br>discrepancy
|-
| '''28''' || __&nbsp;''(+__)'' || __&nbsp;''(+__)'' || __&nbsp;''(+__)'' || __&nbsp;''(+__)'' || __&nbsp;''(+__)'' || __&nbsp;''(+__)'' || __
|-
|}

=== Machine guns ===
{{Specs-Tank-Weapon|2}}
<!-- ''Offensive and anti-aircraft machine guns not only allow you to fight some aircraft but also are effective against lightly armoured vehicles. Evaluate machine guns and give recommendations on its use.'' -->
{{main|M2HB (12.7 mm)}}

''Offensive and anti-aircraft machine guns not only allow you to fight some aircraft but also are effective against lightly armoured vehicles. Evaluate machine guns and give recommendations on its use.''

{| class="wikitable" style="text-align:center" width="50%"
|-
! colspan="5" | [[M2HB (12.7 mm)|12.7 mm M2HB]]
|-
! Mount !! Capacity (Belt) !! Fire rate !! Vertical !! Horizontal
|-
| || ___ (___) || ___ || __° || __°
|-
|}

== Usage in battles ==
<!-- ''Describe the tactics of playing in the vehicle, the features of using vehicles in the team and advice on tactics. Refrain from creating a "guide" - do not impose a single point of view but instead give the reader food for thought. Describe the most dangerous enemies and give recommendations on fighting them. If necessary, note the specifics of the game in different modes (AB, RB, SB).'' -->
''Describe the tactics of playing in the vehicle, the features of using vehicles in the team and advice on tactics. Refrain from creating a "guide" - do not impose a single point of view but instead give the reader food for thought. Describe the most dangerous enemies and give recommendations on fighting them. If necessary, note the specifics of the game in different modes (AB, RB, SB).''

=== Pros and cons ===
<!-- ''Summarise and briefly evaluate the vehicle in terms of its characteristics and combat effectiveness. Mark its pros and cons in a bulleted list. Try not to use more than 6 points for each of the characteristics. Avoid using categorical definitions such as "bad", "good" and the like - use substitutions with softer forms such as "inadequate" and "effective".'' -->

'''Pros:'''

* Access to HE and HE-VT shells with more than 9 kg of TNT
* Top speed of 56 km/h that it can easily reach
* Good reloading rate of 13.3 seconds, which easily surpasses its counterparts
* Can be surprisingly survivable, usually not taken out in a single shot
* Automatic loading mechanism for the main cannon
* Impressive 75° elevation limit

'''Cons:'''

* Hindered by a limited gun depression of -3 degrees
* The gunner optics have a low zoom level (4X)
* Thin armor, will only stop small arms fire

== History ==
<!-- ''Describe the history of the creation and combat usage of the vehicle in more detail than in the introduction. If the historical reference turns out to be too long, take it to a separate article, taking a link to the article about the vehicle and adding a block "/History" (example: <nowiki>https://wiki.warthunder.com/(Vehicle-name)/History</nowiki>) and add a link to it here using the <code>main</code> template. Be sure to reference text and sources by using <code><nowiki><ref></ref></nowiki></code>, as well as adding them at the end of the article with <code><nowiki><references /></nowiki></code>. This section may also include the vehicle's dev blog entry (if applicable) and the in-game encyclopedia description (under <code><nowiki>=== In-game description ===</nowiki></code>, also if applicable).'' -->=== Devblog History===
Development of the M109 began in the early 1950s under a U.S. program to develop a common chassis for a number of different SPH designs. Upon entering service, the M109 was immediately deployed to the Vietnam War. However, its operational service during the conflict was cut short due to serious mechanical malfunctions which rendered the fleet inoperable. Nonetheless, after being addressed and receiving its first upgrade to the A1 standard, the M109 would continue service with U.S. forces for decades to come, taking part in virtually all military conflicts where U.S. forces were deployed in. Once its design eventually matured, the M109 successfully resisted replacement on multiple occasions and continuously received upgrades until the present day.
== Media ==
<!-- ''Excellent additions to the article would be video guides, screenshots from the game, and photos.'' -->
''Excellent additions to the article would be video guides, screenshots from the game, and photos.''

== See also ==
<!-- ''Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:''
* ''reference to the series of the vehicles;''
* ''links to approximate analogues of other nations and research trees.'' -->
''Links to the articles on the War Thunder Wiki that you think will be useful for the reader, for example:''

* [[M109G (Italy)]]

* [[M109 (Israel)]]
* [[M109A1 (Great Britain)]]
* [[M109G]]

== External links ==
<!-- ''Paste links to sources and external resources, such as:''
* ''topic on the official game forum;''
* ''other literature.'' -->

* [[wt:en/news/8537-development-m109-the-king-of-battle-en|[Devblog] M109: The King of Battle]]
{{USA tank destroyers}}