@shell70634 ,
Your response comes thru a little harsh.......this is the friendly machinist forum.
Sure let's warn about the complexity of the task, but let's also provide something useful too.
@MaryCHughes ,
Much depends on what you want to accomplish.
Are you after chasing every bit of accuracy when shooting?
Do you want to learn reloading?
Are you after keeping guns in show-room condition?
Are you interested in how to appropriately clean you guns without doing damage?
If you provide some direction, then people here will help you hit your target.
There are some interesting discussions going on here.
Here's one:
https://www.hobby-machinist.com/threads/borescope-results.93819/
the main discussion is about setting expectations for what a new barrel should look like on close internal examination.
However the thread also gets into cleaning regimens and some subtleties of competition shooting.
Here's another about how to best fill some holes:
https://www.hobby-machinist.com/threads/filling-in-scope-mount-holes-in-a-receiver-barrel.92338/
You are welcome to ask anything you want here.
The more detail you can give the better the responses will be.
Welcome to the group!
-brino