The rifle bore (that's the inside of the barrel that the bullet goes through, for the newer folks to this sport) is one of the main things to consider when we start talking about precision accuracy. Without going too deeply into advanced internal and transitional ballistics, let's just say that the internal condition of the rifle bore changes over time.
Here's what you can expect from a standard of the shelf rifle bore over time.
1. "Virgin" = Brand new. Less than 5 shots through it. (Some factories do this for Quality Control)
2. "Broken In" = Has over 60 or 70 shots through it. Has been cleaned.
3. "Seasoned" or "Equilibrium" = THE sweet spot. The most accuracy that your barrel bore can give you.
4. "Excessive Fouling" = Accuracy drops off quickly. Groups go haywire.
There are 8 million ways to "break in" a rifle barrel and I doubt that too many rifles chambered in .22lr will even have a recommendation for breaking one in. Most bore and barrel "break in" procedures are done for rifles that are being put to use for long (0-800m) and extreme long range (1000m+) applications. I actually have a blog posting (not necessarily for the ARM series) that shows how I broke in my XLR rifle.
What you need to know is that it isn't "necessary" to break in a rifle barrel. They tend to break themselves in, over time, anyhow. Could it hurt to take a little time and break one in? Heck no.
But I honestly didn't break in the Mossy 702. I just cleaned it up really good, took it out and started throwing copper. ALWAYS clean a brand new bore or a bore unknown to you. You never know where it has been.
My Cleaning Regimen:
I clean a brand new barrel very aggressively with Hoppes #9 mild solvent and a bore brush. A new barrel WILL have some type of lubricant/preservative in it from the factory. It will also have machining imperfections that you can not see. Going after it with some applied and controlled aggression and a bore brush gets that gunk and junk out of the bore and might smooth some of those imperfections out a little bit, whether you can see it or not.
**Claymore's Recommendations** Use a coated 1 piece cleaning rod...NOT the 3 piece rods that come in most inexpensive cleaning kits. They have a tendency to break at the worst possible moment and ruin things like the bore, the crown, the throat.
Also, be VERY careful around the Crown (the very end) of your muzzle and the Throat (the part just before your bore starts in the receiver end...where the bullet goes IN). It's not hard to damage those two areas. Be careful.
So, new barrel, soak a patch in mild solvent like Hoppes #9, run it slowly through the barrel and then back again, once or twice. We are trying to make sure that the bore is saturated with solvent. Let the barrel sit/soak for a few minutes. Now we put the brush on our rod and get busy with about 5 strokes in each direction, being careful around the crown and throat areas.
**Side note, some folks do NOT like to go backwards (muzzle to receiver) with their brush or patch. It is all personal preference as long as you are careful.
After the brush, run patches through the bore until they come out clean and dry. It could take 3, it could take 13. After they run clean, you are good to go do some shooting.
At around 60 shots or so I will clean the bore again. I will clean it the same as the first cleaning. Aggressive, yet careful.
After that, I won't introduce ANYTHING into the bore of that rifle until such a time as I see that my shot groups going in the wrong direction....when they get worse it is time to clean it. .22lr isn't the cleanest cartridge ever developed, that is for sure. There's quite a bit of residue left in the barrel, so on and so forth.
Accuracy IMPROVES as the bore develops "fouling". Each time the bullet goes down the barrel, it leaves some copper fouling and some powder fouling in its wake. Some fouling is GOOD for a bore. It builds on the walls of the bore, decreasing the area around the projectile and increasing the pressure pushing the bullet without escaping around it as much.
Real world scenario that I encountered while doing the testing for Pt. 4. - My rifle had been printing some really nice 3 round groups, averaging 1/4". You can see in the pictures from Pt. 4 that there are 3 rounds very tightly spaced and typically the group opens up a little with shots 4 and 5. So, I get ready to get some groups for my data, and low and behold I can't get a group worth a flip, with either brand of ammo that I had been working with.
My first attempt at a group was this...what initially caught my eye was how high the grouping was and the spread made me wonder a little bit, as well. I wasn't too concerned being my first shots of the day.
Here's the second attempt for a 5 shot group. Since group one wasn't what I consider to be "on par" with my expectations, I slowed down, went through my shot routine with serious purpose, and got this one. More spread, still printing high.
I loaded up with a full 10rds in the magazine. I had a sneaking suspicion that my muzzle velocities were going up up up and that it was close to time to clean the powder fouling out of the barrel.
Just to be sure that it wasn't me goofing things up (I tend to check myself first, equipment second) I walked away for a while, then came back to the rifle, loaded three and settled in for some serious shots down range.
This is the straw that broke the camel's back. That, my dear friends, is a 3 shot, 3" group.
Quick remedy. I love bore-snakes. No rods to break, no nasty sharp spots to damage crowns and throats. I dig 'em. Big time. A dab of some Hoppes #9, down goes the snake, out it comes. One more time to dry things out and done. Powder remediation in a jiffy.
But that's not all, folks. After you clean the powder fouling your rifle will NOT be back to normal yet!!
Here are the first 10 shots after a quick powder cleaning. I actually made sure to really try for good grouping just to see how bad it would really be...The first two shots were the ones on the far right and the one that is just high and to the left of the 4 ring.
I had hopes that after 10 shots that things would calm down a little bit. Here's the next 5.
With all rounds printing inside the 4 ring, I was a lot more confident that things would steadily improve, back to where it was shooting before I cleaned it. The next 5 rounds told me it was back to normal and time to rock and roll.
Please keep in mind that this cleaning regimen and these results are for a store bought sporting rifle, not a bench rest target rifle. The serious target shooters have special regimens, break ins, cleaning routines, and voodoo ju-ju that are not required by a fun loving recreational plinker like myself.
For my fun rifles, to get the most out of them as I can, I don't mess with the bore until it needs it.
Don't mess with a streak.
If it ain't broke, don't fix it.
If it groups well, don't clean it.
Only YOU know your personal groups and your personal averages. Soon we will be getting into the Art of the Shot and some of my routine that may help you improve your groups a little.
Hey, if anyone has a suggestion that can help the masses or even a pointer that I can use in MY shooting, feel free to comment. I am always open to try new methods and learn new things.
My methods aren't always the traditional or the "right" way, they are more of a hybrid conglomeration of things I've learned through various sources that have worked well for me over the years.
I always want to improve. Always. Never accept being mediocre if you are passionate about something.
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