Youtube, youtube, youtube.
Buy a cheap ass lathe and start watching people like:
mrpete
abom79
oxcotool
etc
There is more info on basic lathe operation on youtube than any trade school. CNC is another matter.
mrpete is a retired shop teacher and abom79 is a journeyman machinist who is an excellent teacher making excellent videos, especially on threading if it is an area of concern.
All of this information is very good as is the info from the others replying to the OP. The thing is, it depends a lot on how much basic knowledge the OP has concerning lathes and their operating parameters.
What seems straight forward to many here is a complete mystery to many.
A lot of people are immediately lost by nomenclature or terminology relating to lathes and other metal working machines. In many cases it's VooDoo magic. That's why I suggested a MENTOR.
Online stuff is great, once the new operator understands his machine and its components.
The old style lathes/milling machines were pretty simple as far as levers and back gears/quick change gear boxes went. Also a basic understanding of mathematical equations and understanding ratios etc is a great aid to manufacturing a part from a piece of round stock, square bar or a rifled barrel blank.
Another issue is that the machines being worked on by the people in the youtube videos LOOK COMPLETELY DIFFERENT in comparison to the machines being used by hobby machinists. The dials and levers are in different locations and sadly, many of the Oriental machines don't come with manuals. The manuals are often available online but if you want or need a hard copy to take to your machine as a reference, you will have to print it yourself.
Cutting chips???? Great advice to a point. Most newbies have no idea what tooling they need to cut those chips. They also don't have any bits of scrap to practice on or access to it, so tend to head for a supplier and purchase expensive stock. A length of cold rolled or even black iron to practice on can cost an easy $20 for a foot long piece. A piece of scrap can be picked up at a scrap metal dealer for a few dollars.
I picked up a length of 1 inch stainless round stock that was 4 feet long last spring for making stainless muzzle brakes. The supplier wanted $60 for a 3 foot length. I went to a scrap yard and found a four foot length for $10.
The OP, is under the impression that he can just learn the basic steps to turning out match barrels for his actions and not have to learn anything else. Those of us that know better are trying to explain this just won't happen.
To the rest here in a similar situation, I have a bit of advice. IF YOU CAN'T FIND a willing mentor, watch the online videos to at least get an idea of what SHOULD be happening.
FOR GOODNESS SAKES, LEARN THE BASIC SAFETY PRACTICES. Such as don't leave chuck keys in drill press or lathe/mill chucks. Darn those things hurt when they bounce off your forehead.
Wear sleeve covers or wear short sleeve shirts. It's amazing how fast your arm or hand can get wrapped around the piece you're working on. Fingers and even hands can be PULLED OFF, even by relatively low horsepower machines. I saw a fellow lose his middle finger on a drill press because he refused to take off his cotton gloves and the finger got caught on a sharp edge.
These machines only do what they are designed to do. They don't think. They don't care who you are or who you think you are. They don't care if your handsome or handy. If you do something stupid, they will bite you. They don't know and don't care.
When you push the START button or throw the ON switch, don't rest on the machine. People do this sort of sh1t and get HURT. Don't rest your hand or body on the material you're working. YOU WILL GET HURT.
I know all of this seems obvious but even experienced trades people get bit hard because they did such things while being distracted in one manner or another.
EVEN the SLOWEST SPEED on these machines is blindingly fast when you get caught in them. For GOODNESS SAKES, DON'T FORGET ABOUT YOUR HAIR. Even hair a FEW INCHES LONG can get caught. I saw a lovely young lady lose half of her scalp one morning because she didn't put on her cap before leaning over a piece being turned for her inspection machine. Whose fault was it. It was the operator's fault because she shouldn't have been anywhere near that machine while it was operating. She was an attractive distraction and he forgot basic safety practices and she wasn't aware of them. She was lucky and they managed to reattach her scalp but she will never be able to sport a short hair cut without the nasty scar being visible.