Why does Barrel fowling spoil accuracy

[Mikecr]

I'm content to let the barrel tell me when it needs it

So are the rest of us.

 

[fastfire57]

Mike, if you'd be so kind, please point out where I said that the barrels didn't foul? They did. But it didn't degrade the accuracy like I expected it to, which was a fair bit of a surprise to me. I routinely cleaned every 40-50 shots, simply because I'd always done it that way, and that was the routine I'd gotten into. Over the years, that became more or less standard protocol, simply by repitition. The point to doing this series was the fact that I'd never let one go that far, and wanted to see what happened. I'm not alone here, either. My friend Derrick Martin once shot an entire season without cleaning his bore, just to see what happened. End result? Absolutely nothing. He shot the same High Master scores (an average of 97% or above) throughout the season, just like when he regularly cleaned the rifle. I seem to recall that the late Warren Page onve did the same thing with one of his BenchRest rifles, and found much the same thing. I think there's some historical reasons for why these claims were originally made (and they WERE valid at that time) but have simply been parrotted by gunwriters and shooteers ever since, even though it's no longer nearly as critical now as it once was. Sorry to slaughter the sacred cow here, but there it is.

I shot an average of 400-600 rounds a day, normally six days a week, for over twenty years. Cleaning every 40-50 rounds (as I did), that's a bunch of cleaning. All barrels are slightly different, but they are usually fairly similar in how they behave. I cited a specific example, naming both the barrel make, chambering and twist that I ran the test with. Given a larger cased cartridge, the results may have been a bit different. I recall that when the 7mm STW first hit the scene, there was at least one guy who chambered one up as a 1,000 yard prone gun. Didn't work, due (in his opinion) to fouling issues. You need a cartridge/barrel combination that will go at least 20+ rounds for that game, and his rifle wouldn't do it. Started off fine, but accuracy degraded horribly by the time he got into his second string. Could have been powder foulng, could have been metal fouling, who knows. But it didn't work. Point is, the combinations are different, and need to be handled on an individual basis. You clean all you want, but I'm content to let the barrel tell me when it needs it . . . and don't be surprised if you don't hear from it for a while.

As far as sacred cows go, I like mine rare, and sitting beside a loaded baked potato.

It looks like you have done a LOT of barrel cleaning.
What have you found to be the best for powder and carbon removal and your process for doing so?
I ocassionally use a suppressor on my 223 and 22-250AI but when I do I get a lot of carbon buildup (carbon ring) just in front of the chamber and it is very
difficult with a lot of scrubbing to remove.
For powder removal I use Montana Extreme Cowboy Blend and copper, One Shot.

 

[Bart B]

I agree with Kevin's comments on barrel fouling vs accuracy. Kevin's predecessor at Sierra Bullets often "sang the same song" about fouling. And my experience across several 30 caliber barrels has been the same.

Comments in this thread about fouling changing a bullet's balance are easy to figure out.

If there's a copper wash building up in barrel that started out with bare metal in the bore and groove surfaces, that copper had to come from the bullets. There's no copper in the powder that's deposited on the bore surfaces. As the bullet's lost some of its jacket material, it makes sense to me that it's not uniformly removed around the bullet. The bore surfaces are rougher in some areas than others. As more copper's rubbed off the bullets and imbedded into the micro pits and valleys, the "landscape" smooths up. Eventually little or no copper's removed from subsequent bullets and they remain well balanced as the leave the muzzle. All of which is why it takes a few to several shots to get a rough bore smoothed up to where all the bullets arrive at the same place downrange. But they're not quite as accurate as bullets fired from barrels that have the least copper fouling isues.

Hardened powder fouling typically doesn't remove jacket material from a bullet, but it can microscopically change a bullet's shape. A barrel maker told me that it sort of swages down the bullet diameter unevenly around it. Smoother surfaces on the lands and grooves tend to powder foul the least. Powder fouling and residue from a previous shot's drug out with the bullet and carried down range. Bullet holes in target paper wouldn't have dark grey colored edges if there was no powder fouling on the bullet that got rubbed off of it as it passed through the paper. And smooth barrels typically don't get built up layers of powder fouling; it stays constant for dozens of rounds.

Best example of how little powder and copper fouling really effect accuracy is the precision test barrels used at Lake City Army Ammunition Plant testing 30 caliber bullets in match ammo. The ballisticians will start out with a squeaky clean barrel aimed at the 600-yard target. Then shoot a couple hundred rounds 30 seconds to a minute apart. Good lots of National Match ammo will have all their bullet holes inside 6 inches. Having seen a couple of those targets, they are impressive for what mass produced ammo from high speed machines will make. And that a good barrel will shoot a bunch of rounds very accurate without cleaning.

In another test with a Hart barrel in .308 Win., a dozen or so 10-shot groups with Lapua 185-gr. FMJRB match bullets all go under 1.5 inches at 600 yards. Then a 40-shot group had all bullets under 2 inches. Barrel wasn't cleaned for those 160 or so shots.

It's my opinion that while copper and powder fouling will happen, if its minimal and consistant throughout the bore, excellent accuracy will happen for many, many shots. Bullets fired through fouled barrels that ain't unbalanced will shoot very accurate.

 

[kranky]

Great post Kevin. I can relate.

A few years ago I took a group from my organization out to David Tubb for a week of shooting. One evening during the week I asked him about cleaning. His response was that most clean far too often and that every rifle has its own temperment when it comes to fouling. The next day he proved his point. We took our rifles and cleaned them and then shot through an Ohler. Each rifle was a bit different, but between 12-15 rounds all had a consistant velocity (.300 win mags, 190 and 220gr SMK). Before the 12-15 mark we witnessed 120fps differences in some rifles! I did the same experiment with my custom 338 Lap and my handloads through my PVM and had the same results. It was starting to make sense when confirming a zero after cleaning some of my work rifles, I could literaly watch the impacts walk right back to the origional zero. For the past few years I have only run a patch through my barrel after a day of shooting, or cleaned and fouled if the threshhold of that particular barrel had been met, for this effort my rifles have been far more predictable and accurate.

Tubb on the subject of cleaning itself- When you clean.....CLEAN!, use an aggressive compound that will get all the copper out of the barrel. He used Sweets 7.62 and an oversized bore brush on his rifles and said just be sure to get it all out. I think he cleaned every 200-300 rounds on .30 cal and above.

Just thought you guys might want the professional opinion of an 11 time national champ.

 

[Iron Worker]

I use KG1 for carbon and copper then is needed follow up with KG12 for Copper . Its gets it all.

 

[RMulhern]

Birds in your barrel spoil accuracy every time!

 

[barnesuser28]

Birds in your barrel spoil accuracy every time!

Haha it took me a second to figure it out but then i caught it.

 

[RMulhern]

Kevin

+1 on your post!

Oh...thanks again for the Lapua caps! Met you on our trip to Kansas when we were going turkey hunting and you were headed to Mesa!

Take care!