Chuck Wendig is entertaining and informative. Guns are cool things. (I will not be dragged into a gun control debate here, so please take that somewhere else.) I am in awe of most things with moving parts, and guns are delight in that regard.
If you are writing a character who uses a gun, there are things you should know, because there are gun fans in every audience (yes, even contemporary YA romance) and they will contact you when you get something wrong. If you don’t have the good fortune to live with walking firearm database who maintains a properly secured collection of guns you can handle, then the least you should do is read Chuck’s post.
And if your model on your cover has his/her finger on the trigger of a gun, THIS gun fan will twitch. Just saying.