The 7-inch RML gun was developed in 1865 to replace the 7-inch RBL gun which had fallen out of favour. The first two marks of this gun were produced by the Armstrong production method, but from the Mark III onwards a cheaper Woolwich design was used. The variants produced:
- 7 tons, Mark I to Mark IV
- 6.5 tons, Mark I to III
- 90cwt gun






