I clean only when the rifle performance is unacceptable.
Agree.
The main takeaway for the beginners... is how do it know?!?
I am waiting for some visitors to get ready to roll, so I will kill a few words for the sake of the beginners.
TLDR: Rookies must shoot well enough and long enough to learn when and how to clean. Using an "inexpensive" varmint/target rifle in something like 223 is a good and affordable way to learn.
At some point in life, a rookie needs to make a decision about how much resource they will burn shooting and what their goals will be for that shooting.
Lets face facts, most of you are not trust fund babies, and have day jobs, a wife, kids, family, households, vehicles, homes to maintain, taxes to pay, etc... and only so many hobbies and opportunities. It is different for everyone, but similar in many ways too.
There is nothing wrong with starting with airgun and/or rimfire in your shooting journey.
Anything that helps with fundamentals and trigger time that is inexpensive and doesn't take too much time is a good thing. But at some point, these don't teach us everything that centerfire does, and it doesn't teach you about centerfire cleaning intervals.
Even folks who don't or can't reload, may want to get to their goals but might not have a good mentor or club nearby.
Don't let that stop you, but don't fall for the internet hype and try to reach the stars before you learn to crawl.
Try to balance between having fun and staying organized. If you skip one or the other, you will likely quit.
That means keeping yourself honest with a journal and shooting a standard recorded target often.
Parts of shooting can be a lot of fun, but let's face it, taking notes is one thing, and cleaning is yet another. Nobody I know likes cleaning rifles.
Nothing wrong with getting started with factory ammo in a medium or higher energy cartridge like a 6.5 CM, but I am taking up space for a moment for the sake of those who are trying to learn this on their own.
Nothing wrong with getting a higher energy gun, but don't skip the fundamentals because it will just take you longer and cost more to get up the learning curve, especially if you are on your own.
To develop a rifleman in a MIL/LEO world, we expect to burn at least 5000 to 10000 rounds to get them to proficiency level. Sure there have been prodigies that ramp up quick, but most kids will fall in the middle of that range to call them proficient.
In that world, there is an organization with resources and mentoring behind their training. Most of the program is out of their hands and the homework has been done for them. They shoot what we tell them, when we tell them, so they clean when we tell them to start out. Later on, we let them explore the boundaries and challenge the concepts on their own.... however they can shoot by then.
But what about you, who doesn't have that and just want to get shooting? How do you know when and how to clean?
As you get rolling in life and want to run a higher performance cartridge, don't forget to start with those fundamentals and find room in your life for a decent heavy bbl 223 and
plan to shoot it a lot. Even folks who have family backgrounds or lots of resources and friends can benefit from running more trigger time with a good training centerfire rifle that gives honest feedback for a fraction of the cost of shooting bigger guns.
You can start with something like a factory Sendero, Savage, or inexpensive varmint or target rig. You just need to have a decent rig/ammo so that you can even tell when fouling is an issue.
Be patient if you are on your own. It takes a while to shoot well enough to establish a baseline, and that is the only way detect that you went past the shot count and need cleaning. At some point you need to allow yourself to shoot into this performance drop-off more than a few times to be able to understand your cleaning interval.
You need a journal and record of your DOPE. You will benefit from a borescope and chronograph, but you can certainly postpone those and get started with just a journal.
Even loaded with the cheapest target rounds and shooting rapid strings, this barrel will run at least 2500 rounds or more before it starts to fail you during rapid strings and eventually won't group in slow fire. To know for certain you are either fouled or eventually worn out, you test a rapid string and you will see the group open up or the zero shift, or both.
I am recommending this type of pattern so that you can run for 15 to 20 shots without taking a break. You will be able to focus on driving the gun and reading the wind, then take your break and let the gun cool off.
A 223 heavy bbl rig can handle that, a skinny higher energy gun cannot. Shooting enough rounds to become proficient in 223 can be done for a fraction of what it costs to shoot the bigger guns.
Plan to burn through about two or more of these bbls on average before you think you know anything about shooting, wind reading, reloading, cleaning, etc..
Any decent inexpensive varmint or target 223 can be the platform for learning how much and when to clean, and what you can or cannot get away with. You can blast, plink and have fun with this,
but always keep a journal and include standard targets at intervals that will tell you when/if performance falls off.
Shoot this year round in different conditions and especially when conditions are "bad". This will keep you honest and teach you without breaking your fun money account.
A 223 that throws 69 to 77 grain bullets uses about 24 grains of powder per shot. When you shoot the higher energy cartridges, you will be burning much more powder and throwing more bullet per shot, and the cleaning interval may look a little different as a result.
The benefit of using that 223 so much, is that you will have learned that powder and copper fouling act different for different bullets and powders, as well as how a higher quality barrel responds. Starting with a inexpensive factory hammer forged barrel, and then replacing it with a high quality cut-rifle barrel, will make you appreciate those differences.
This pattern of rifle and shooting will teach you about more than cleaning intervals, and it will keep you honest without breaking the bank. Good Luck , YMMV