Production began in 1974, with the first version of the gun, known as the L/44 as it was 44 calibres long, used on the German Leopard 2 tank and soon produced under license for the American M1A1 Abrams and other tanks.

莱茵金属Rh-120坦克炮是由西德莱茵金属探测公司设计和生产的一种120mm滑膛坦克炮，是为响应苏联在装甲技术方面的进步和新型装甲车辆威胁的发展而开发的。

此坦克炮口徑為120毫米，可分成早期型44倍徑的L/44型，和後期型55倍徑的L/55。 Rh-120滑膛炮的炮管採用 電渣重熔 製造技術，炮管內壁鍍 鉻，炮管上有排煙器。 早期型的L/44在使用壽限内可發射650發炮彈，火炮後方採用直立楔式砲尾結構。 為了進一步提昇Rh-120的威力，萊茵金屬公司在L/44型号的基础上研发出加長火炮身管长度至55倍徑的L/55型。 L/55的身管长度由L/44的5.28米增至6.6米，L/55型可以兼容發射原本L/44型的所有炮彈，亦可发射专门适配其的DM53/63/73 …

Consolidating the 120mm technology leadership there has been in the last decades a huge enhancement in the Rheinmetall weapon ammunition system leading to advanced ammunition family generations as well as advanced generation of the origin L44 weapon with longer barrel (L55) or muzzle-brakes in order for mounting on medium combat platforms.

The M256 is an American 120 mm smoothbore tank gun. It is a licensed-built German-designed Rheinmetall Rh-120 L44 gun tube and combustible cartridges with an American-designed mount, cradle and recoil mechanism. It is primarily used by the M1 Abrams main battle tank.

一项名为Neue Panzerkanone 的140mm新型坦克炮计划胎死腹中，研发方向重新回到120mm口径，催生出更先进的L55坦克炮。 L55基于L44相同的后膛结构和系统接口，相同的内部几何结构，将主炮长度增加1.3米（4.3英尺），赋予炮弹更长的加速时间，从而提高初速。

2023年8月13日 · 中国为89式120毫米自行反战车炮研发了两期尾翼稳定脱壳穿甲弹，可和Rh-120通用。 操作国家 L/44 德国：豹2型坦克（A1至A5） 美国：M1A1/A2艾布拉姆斯（使用改进自Rh-120并获得特许生产的美制M256主炮） 日本：90式坦克、10式坦克（使用由日本制钢生产的改进型90式/L44 ...

Production began in 1974, with the first version of the gun, known as the L/44 as it was 44 calibers long, used on the German Leopard 2 tank and soon produced under license for the American M1A1 Abrams and other tanks. The American version, the M256, uses a coil spring recoil system instead of a hydraulic system. [3] .

As the standard NATO smoothbore gun for main battle tanks Leopard 2 and AbramsM1A1, Rheinmetall’s L44 tank gun proved superior to all rivals in the 120 mm arena.

2022年10月27日 · It was tested on the British Challenger 2 as a potential replacement for its current weapon, the rifled L30 120 mm cannon. A variety of ammunition has been developed for use by tanks with guns based on Rheinmetall's original L/44 design.