Are there any good resources for people using the firearm as a method?

[Trashcan]

So there's tonnnns of information on regular firearms, but not a lot on black powder rifles which is my chosen method. But I know people have used this method before and succeeded. Not a lot of people on here seem to know a lot about firearms (and that's ok, I don't either). I'm just wondering if there are any good resources about using firearms as a method? Even if it doesn't touch the black powder rifle? Something that can talk about the different bullets maybe or the exact angle needed to hit the brain stem. Just so I can use that to get a pretty good idea on what to use.

Thank you everyone in advance.