This is part of an article I wrote for Len, should appear next month but since it was brought up, I think this portion applies to the topic. Reference custom barrels.
Barrel brake in;
This could be the most debated subject of barrel care. The two schools of thought are, just shoot it, or shoot and clean for x# of rounds. I have tried both and from my experience the proper way to go is the shoot and clean, this is why.
It is a well known fact that a barrel, even a custom lapped barrel will attract more copper fouling to the bore on the first few bullets down the tube. The single most important reason to shoot one and clean out that copper fouling, is to prevent a build-up which will be MORE difficult to remove if multiple bullets are fired down the virgin bore. Yes we may clean it five times with 5 bullets fired, but you will notice that the fifth cleaning was much easier than the first. On the other hand if we fire 5 bullets in succession we will have multiple layers of copper laid down, which will require more cleaning to remove. My opinion is that the 5 cleanings will leave your bore in better condition than the single cleaning after 5 shots. I have shot, bore scoped, and cleaned a couple of barrels during the brake in, and the visual bore inspection was quite enlightening. So what is happening as these first few bullets pass down the clean barrel? Good question answers range from; burnishing the surface of the barrel, smoothing out the throat, to depositing carbon in the grooves of the micro finish. I cannot say for certain, but the results of a broken in barrel do have a noticeable effect. Now all this is not to say a barrel that had 20 rounds fired down it right from the start will not brake in. I feel the barrel will get there quicker with fewer rounds and less scrubbing, cared for the way I have outlined.
Now not all barrels will act the same, the surface finish, steel type, hardness, cartridge, and lubricity, can all affect the barrels ability to “brake-in” so none of this is set in stone. You may find that your barrel cleans up easily after 3 shoot and cleans, another barrel may take 12 shoot and cleans.
One other overlooked aspect is the period of time in which the barrel stabilizes. Now don’t read more into this than what I’m saying. But if you load 75 cartridges exactly the same and fire them through a new bore. At the same time you did a few shoot and clean, and the barrel is cleaning up easily. You will notice that the velocity readings of these 75 bullets may be a little erratic, and will most likely increase through this period of use. After the 60th or so bullet the velocity readings should equalize and may be up to 50 fps faster than the first 20-40 bullets. This was not my finding, but pointed out to me by a friend who has broke in many more barrels than I, since that time I have seen it enough to believe it.
My procedure is exactly this; Shoot one round, remove all copper, one dry patch, one wet patch of Kroil, one dry patch, repeat about 5 times total. Shoot 5 rounds, remove all copper, one dry patch, one wet patch of Kroil, one dry patch. At this point 95% of the barrels I use will be cleaning up extremely quick and easy, and I will begin some form of load development. I will usually try and get another 2 cleanings in the next 50 rounds or so, and monitor the progress with the bore scope. After this I consider cleaning to be routine and will follow the advice in the second paragraph bellow.
You'll have to wait for the rest of the story...