Subject
2 free books about gunnery, free to read online. Chapter 1 of any book is free, no account needed.
Gunnery in 1858: Being a Treatise on Rifles, Cannon, and Sporting Arms Explaining the Principles of the Science of Gunnery, and Describing the Newest Improvements in Fire-Arms
William Greener
The Gunner's Examiner
Harold E. Cloke
