Every historical author needs at least one good expert source. One of mine is 'Hawkeye', a British gun-dealer and expert on Civil War period firearms.
I recently sent him a few pages of my first Western Mystery, to make sure I had details of the guns right.
In the first Western Mystery, The Case of the Counterfeit Injuns, my hero gets shot with a Smith & Wesson seven-shooter. It's only a .22 but my hero is only a kid. So how much damage would it do? Would a slug from a .22 knock down a 12 year old if fired at close range? Would it pierce buckskin? Or just bounce off? Can you even call a .22 a slug? Shouldn't you call it a 'pea'? It's tiny! (above)
I sent the relevant pages to Hawkeye and he sent back this fascinating reply:
I did a little test for you myself. Taking 10 rounds of modern .22 short, I pulled out the bullets, tipped out the modern nitro powder & replaced it with 4 grains of fine black powder, then put the bullets back on top. Fired from the old Eureka - barrel length 2 1/2 inches, it penetrated 1 1/4 inches of pine at 6 yards range. At the same distance it penetrated a soft leather belt pinned to a new bar of soap and exited the rear of the soap through a large hole. In my opinion the Smith & Wesson No. 1 with its 3 inch barrel would perform almost identically.
(above: Hawkeye's 2 1/2 inch barrel Eureka)
Ouch! So the answer to my question is yes, you can call a .22 ball a 'slug' because it can pierce buckskin and make a nasty hole at close range!