+ to whatever everybody else said, first of all.
In order to also create space for newbies and beginners to the sport, I would also include reviews of stock, market firearms as well. It seems that 2017 can very well be the Year of the Bolt Action. Just two Cabelas catalogs 4 weeks apart featured about 5 new models of bolt action rifles. The Remington 783 looks like it is going to be popular this Christmas. Low priced, available in a world of calibers, and easy to use. And there is a new Thompson-Center bolt action that is released in the $300-400 price range. I never even knew TC was going to make a bolt action!
So I am predicting this new year, there will be a lot of people who received rifles as presents who will want to watch tutorials on how to properly use and care for them. And there will be no better thing on a gun channel than reviews and range reports on currently popular factory guns. For the more advanced audience, tips on accurizing, glass-bedding, scopes, gunsmithing etc... would be another good subsection to have.
But with all these new rifles coming onto the market, the Staples order-supervisor part of me from years ago is kicking back in full swing, and I am predicting there will be a considerable number of newcomers to the shooting world, including those who have never even handled a firearm before. Good luck with your channel guys, and thank you for doing your part to educate the world-wide Youtube community on firearms.
I'd like to learn how to do hot salts bluing to make my cap n balls have an original style finish.
You can also try carrying them all the time, drawing and shooting them, in all kinds of weather conditions, for many years. It will take slightly longer than doing a salt-blue job but all the guns you see in Old West museums that have the patina finish, I am sure they didn't get that way because their owners modified them