Go read articles on 6MMBR.com http://www.6mmbr.com/articles.html the benchrest shooters site and Dan Lilja's library.
I manufacture barrels, bolts, extensions and muzzle devices, been in and around the business since the 70s.
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Go read articles on 6MMBR.com http://www.6mmbr.com/articles.html the benchrest shooters site and Dan Lilja's library.
I manufacture barrels, bolts, extensions and muzzle devices, been in and around the business since the 70s.
I've heard both sides of this... my personal experience in precision class was that the carbon build up, after 20-30 rounds started hurting accuracy.
At no point did we deal with copper fouling... but the carbon removal upset the gun for about 3 round and then it went back to shooting original point of aim.
I do try to keep copper build up at bay in my Bolt with some Boretech Cu2 every 100 rounds or so.
Depending on the condition of your throat, the interaction of cartridges loaded with different propellants (requiring group "Settling") might be attributed to the coatings used on the different powder granules (as well as their shape).
Starting with a ball propellant (nitrocellulose single base powder like WC844 and/or H322), followed by a double-base stick propellant (nitrocellulose and nitroglycerin, like VV N540) may show rough groups as any burn retardants interact with the coatings on following rounds -- until they're burnt out of the barrel.
Throw in an additional spin by using something like Copper Fouling Eraser (CFE used in Hodgdon powders, originally designed for the military's all-copper or bronze bullets) and you add a new twist to your math.
This article was published in the March, 2000 issue of Precision Shooting Magazine. It was written as a respose to a query by Editor Dave Brennan in reference to a rifle barrel fouling article written by Fred Barker which was published in the February, 2000 issue of Precision Shooting. DL
Barrel Fouling
By Dan Lilja
I read the excellent article by Fred Barker on fouling and accuracy in his 6.5 caliber 1000-yard type rifle. Per your request I'll do my best to convey my thoughts and observations on rifle barrels and bullet fouling.
It has been my experience in shooting a number of rifles and barrels used in 1000- yard rifles, that longer barrels and faster twists tend to foul more. And as Fred pointed out, this could be caused more by the long bullets (and the internal forces acting on them) than the barrel. I found too that some bullets just seem to foul more than others. This is no doubt caused by differences in the gilding metal used to make the jackets.
Fred makes some important observations and distinctions between true high-quality custom barrels and production barrels. I liked and agreed with his comment that " . . . in poor quality, mass-produced barrels, that build up thick, rough fouling and shoot poorly, every shot is a flier." One of the big differences between these barrels is the internal finish. A rough barrel is going to foul. After looking at the differences between a production barrel and finely finished lapped barrel in our video borescope, a customer made the comparison that the production barrel looked like railroad ties and the lapped barrel like a mirror.
Makers of custom hand-lapped barrels spend a lot of time achieving the internal finish that they require. We've experimented with different techniques and products and have settled on what we believe gives us the best finish. We strive to get a smooth uniform finish without losing the geometry of the rifling -- that is, keeping the lands sharp-cornered and crisp. And though it may surprise some, lapping to a finer finish will result in an increase in fouling. A barrel can be too smooth.
We've had customers ask about aftermarket operations and procedures that will "improve" the interior finish of our barrels. And I always warn them against it. The thought of lapping with 1200 grit makes me cringe. And I also feel it is very desirable to have the direction of the finish lay parallel to the rifling. A finish like this is produced naturally with hand-lapping. Some procedures can and will produce a directionless finish. My advice is to leave the internal finish to the barrel maker. Trying to "improve" it is only going to make it worse. The exception being unlapped production barrels.
I've noticed too that given an equal interior finish in both stainless steel (416) and chrome-moly (4142), the chrome-moly barrel will copper foul more.
I have not seen any real reason to use a dry lubricant on bullets as an effort to reduce fouling. With a proper barrel break-in, a top quality lapped barrel, and normal cleaning procedures, fouling just does not appear to be a major problem. We have now available some excellent bore cleaners that do a great job of removing the powder and jacket fouling that does accumulate. My personal favorite is Butch's Bore Shine.
It is important to break-in a barrel though. The jacket material must be removed after every shot during the initial few rounds. If this isn't done the areas of the barrel that fouled will tend to pick up more fouling and it will build on itself. It is important to get a layer of powder fouling on top of the lands & grooves. This hard deposit will prevent the copper from stripping off the bullets. However, if the internal finish of the barrel is too rough the barrel will never be completely broken-in and fouling will always be a problem. Some barrels can't be broken-in.
A similar phenomonon can exist if the shooter uses an abrasive-type cleaner too often. The abrasives are very effective at removing all traces of both powder and jacket fouling. I mentioned that a barrel can be too smooth. The abrasives can get a barrel too clean as well and in effect the shooter is rebreaking-in the barrel again every time he cleans. This can end up in the dog-chasing-his-tail scenario. The shooter thinks the barrel is a fouler, as evidenced by the copper accumulations in the barrel. He works hard at removing the copper, resorting to using an abrasive cleaner. But when he does he removes the desirable layer of carbon fouling left by the powder and exposes fresh steel ready to grab some more copper off the bullet on the next shot. The cycle repeats itself. Like the dog the best way out is to go lay down and take a nap.
I don't think I agree with Fred that the elements added to the steel to aid in machinability are a problem. At least for the steels we use. We buy our steel directly from the steel mills in truckload quantities and specify the chemistry we want. It is rare to see imperfections in the steel caused by impurities or alloying agents. And if they do show up as blemishes in the lapped finish, I would consider their size insignificant.
I do agree with the premise of Fred's article; we don't know all there is to know about fouling in barrels. But I do think that some of the procedures that have been tried and are still used by many shooters are steps in the wrong direction. Dry lubricants, surface finish enhancement procedures, and the overuse of abrasive cleaners all fall into that category, in my opinion.
Krieger's website-
BREAK-IN & CLEANING:
With any premium barrel that has been finish lapped -- such as your Krieger Barrel --, the lay or direction of the finish is in the direction of the bullet travel, so fouling is minimal compared to a barrel with internal tooling marks. This is true of any properly finish-lapped barrel regardless of how it is rifled. If it is not finish-lapped, there will be reamer marks left in the bore that are directly across the direction of the bullet travel. This occurs even in a button-rifled barrel as the button cannot completely iron out these reamer marks.
Because the lay of the finish is in the direction of the bullet travel, very little is done to the bore during break-in, but the throat is another story. When your barrel is chambered, by necessity there are reamer marks left in the throat that are across the lands, i.e. across the direction of the bullet travel. In a new barrel they are very distinct; much like the teeth on a very fine file. When the bullet is forced into the throat, copper dust is removed from the jacket material and released into the gas which at this temperature and pressure is actually a plasma. The copper dust is vaporized in this plasma and is carried down the barrel. As the gas expands and cools, the copper comes out of suspension and is deposited in the bore. This makes it appear as if the source of the fouling is the bore when it is actually for the most part the new throat. If this copper is allowed to stay in the bore, and subsequent bullets and deposits are fired over it, copper which adheres well to itself, will build up quickly and may be difficult to remove later. So when we break in a barrel, our goal is to get the throat “polished” without allowing copper to build up in the bore. This is the reasoning for the "fire-one-shot-and-clean" procedure.
Every barrel will vary slightly in how many rounds they take to break in For example a chrome moly barrel may take longer to break in than stainless steel because it is more abrasion resistant even though it is a similar hardness. Also chrome moly has a little more of an affinity for copper than stainless steel so it will usually show a little more "color" if you are using a chemical cleaner. Rim Fire barrels can take an extremely long time to break in, sometimes requiring several hundred rounds or more. But cleaning can be lengthened to every 25-50 rounds. The break-in procedure and the cleaning procedure are really the same except for the frequency. Remember the goal is to get or keep the barrel clean while breaking in the throat with bullets being fired over it.
Finally, the best way to tell if the barrel is broken in is to observe the patches; i.e. when the fouling is reduced. This is better than some set number of cycles of "shoot and clean" as many owners report practically no fouling after the first few shots, and more break-in would be pointless. Conversely, if more is required, a set number would not address that either. Besides, cleaning is not a completely benign procedure so it should be done carefully and no more than necessary.
comment- pretty clear they are saying you don't want copper fouling in the bore.
Personal experience: I was a highly competitive small bore shooter in the 70's. We only cleaned our rifles once per year and we shot tens of thousands of rounds per season in our Remington 40x rifles. After cleaning the rifle at the end of season it took a couple of hundred rounds to settle the groups at the beginning of the year. These rifles would shoot 1 bullet hole groups at 50 meters when benched and with match ammo.
I have noticed the same with my high power weapons...especially those with high quality barrels.
If you are regularly shooting a rifle, more barrels are ruined by improper cleaning than are by not cleaning, especially now using ammo with quality non-corrosive primers.
Unless the weapon is headed to the safe for long term rest or living in very humid conditions, all the bore gets is a couple of passes of a clp soaked bore snake after shooting. In all my weapons and years, I haven't lost a a bore to corrosion yet.