1st groups today were tight with my 6x284,after 20 rnds last group of the day ( Same load) were greatly expanded. If I was shooting a 308 I'd still be getting tight groups well after 20 rnds. Both cartridges bbls collect copper. Why is the one more sensitive then the other ? On Military Channel there was a story of a sniper making critical long range hits all day long with his sniper rifle. He didn't stop to clean it ? My 6x284 has a Cut rifled Brux bbl ?
Why does Barrel fowling spoil accuracy
- Thread starter Ironworker
- Start date
Larger calibers do seem less sensitive. When I use WS2 coated bullets I can shoot an entire match without cleaning. Maybe look into that or HBN. I get almost no copper using the coated bullets also. That said, I'm not a fan of moly coated bullets.
Number one, very few people have ever bothered to actually check the accuracy of a given barrel as fouling develops, much less doing so in a scientifically valid manner. We tend to take for granted the "fact" that groups will open up, or go completely to hell if a barrel isn't cleaned completely after, 20, 30, 40, or however many rounds. That's not necessarily the case. To begin with, fouling only goes so far; it's not like your 308 will keep fouling until it becomes a 7-08. They can fire one helluva lot more rounds than most will believe, simply because we hear this stuff repeated so often.
Some years back I was tasked with testing a wide variety of various moly coatings (and similar products) to select the best. As a baseline, since everyone was so committed to the idea that these coatings would allow the shooter to fire so many more rounds without cleaning than uncoated rounds would, I wanted to find out what happens when we run this many rounds of uncoated bullets without cleaning. 300 was a magic number that I kept hearing from the guys who were committed to moly, so that's what I used. I loaded and fired a total of 300 rounds of uncoated 168s in a 308 Win, from a machine rest, in a series of 10 round groups. Simultaneously, each series of 10-rounds groups went into a fifty round composite. All firing was done at 200 yards, in a tunnel, and without ever moving the test barrel from the machine rest. The gun was a 308 Winchester (Obermeyer reamer), using a 1x12" Hart (as I recall) buttoned barrel. When I was done, I had a series of thirty (30) ten-round groups, and six (6) fifty round groups to evaluate. The point here was to see at what point the accuracy dropped off to a measurable (and statistically significant) point. After all the firing, there was virtually no noticable degradation of group size throughout the test. The 50 round composite groups were where things got interesting. In them, they became slightly tighter throughout the test, with the single smallest fifty round group being the last one, shots #251 through 300.
Bottom line here is, most shooters worry way too much about this, and don't really know just how long a good barrel will hold its accuracy.
Barrels are different, and certainly a crappy barrel will often show more fouling than a better made sample. We're talking about differences in the barrel itself here, not the fouling per se. Which is why I have a very simple policy regarding such things; Life's too short to waste time with bad barrels. Use decent quality barrels, and things are just so much easier.
Different calibers (naturally) will show different tendencies here as well, and that has to be accounted and adjusted for. Know that going in, and let that be a factor in selecting your next chambering, if that's an issue for you.
_________________
Some years back I was tasked with testing a wide variety of various moly coatings (and similar products) to select the best. As a baseline, since everyone was so committed to the idea that these coatings would allow the shooter to fire so many more rounds without cleaning than uncoated rounds would, I wanted to find out what happens when we run this many rounds of uncoated bullets without cleaning. 300 was a magic number that I kept hearing from the guys who were committed to moly, so that's what I used. I loaded and fired a total of 300 rounds of uncoated 168s in a 308 Win, from a machine rest, in a series of 10 round groups. Simultaneously, each series of 10-rounds groups went into a fifty round composite. All firing was done at 200 yards, in a tunnel, and without ever moving the test barrel from the machine rest. The gun was a 308 Winchester (Obermeyer reamer), using a 1x12" Hart (as I recall) buttoned barrel. When I was done, I had a series of thirty (30) ten-round groups, and six (6) fifty round groups to evaluate. The point here was to see at what point the accuracy dropped off to a measurable (and statistically significant) point. After all the firing, there was virtually no noticable degradation of group size throughout the test. The 50 round composite groups were where things got interesting. In them, they became slightly tighter throughout the test, with the single smallest fifty round group being the last one, shots #251 through 300.
Bottom line here is, most shooters worry way too much about this, and don't really know just how long a good barrel will hold its accuracy.
Barrels are different, and certainly a crappy barrel will often show more fouling than a better made sample. We're talking about differences in the barrel itself here, not the fouling per se. Which is why I have a very simple policy regarding such things; Life's too short to waste time with bad barrels. Use decent quality barrels, and things are just so much easier.
Different calibers (naturally) will show different tendencies here as well, and that has to be accounted and adjusted for. Know that going in, and let that be a factor in selecting your next chambering, if that's an issue for you.
_________________
Have just recently become "involved" in my first 30BR (Krieger 1-17) and continue to be amazed how easy it is to clean ( as verified with my Hawkeye borescope), compared to the 6ppc's and 6BR's that I've been shooting since 1998, various barrels of course.
I keep thinking, "Is that all there is?", check it with the borescope, yup, it's clean. Wow!
I keep thinking, "Is that all there is?", check it with the borescope, yup, it's clean. Wow!
ironworker,
all good intentions and thoughts - HOWEVER-
it has been provern for years in BR competition 100-300yd that rifles cleaned after each relay give better group record than those notcleaned
if you check any BR club, shooter, rifle maker whose rifles are record holders, you will get this answer
also, go to Hart rifle web page and look up the comments about moly forming in the bbl and the negative of it.
Bob
all good intentions and thoughts - HOWEVER-
it has been provern for years in BR competition 100-300yd that rifles cleaned after each relay give better group record than those notcleaned
if you check any BR club, shooter, rifle maker whose rifles are record holders, you will get this answer
also, go to Hart rifle web page and look up the comments about moly forming in the bbl and the negative of it.
Bob
Killshot
X's matter....but 10s win (but damn, Xs feel good)
Kevin's description of the test they ran is just what we need. Now, can you please do that with four other calibers and a couple of powders each?
Seriously, this type of testing carries significantly more weight than the "common knowledge" of one type of shooter.
Seriously, this type of testing carries significantly more weight than the "common knowledge" of one type of shooter.
In a word, no. I used to be able to do stuff like that, but those days are long gone. Shame, too, since it did used to turn up some surprising revelations from time to time. This was one of those times. Some of those tests did get fairly extensive and very time consuming. I did one on cryogenic barrel treatments that was a blind test using four different barrels, controlled accuracy ammo for verification at various points in the barrels lives, and a total of over 17,000 rounds. Yeah, there were some advantages to that job back in those days.
Different cartridges (various expansion ratios) and different velocity levels will definately effect results here, so everyone needs to rely on their own observations accordingly.
Different cartridges (various expansion ratios) and different velocity levels will definately effect results here, so everyone needs to rely on their own observations accordingly.
BoydAllen
Gold $$ Contributor
Years ago, I had a factory barreled Remington 722 chambered in .222. Wanting to get the most performance, I tuned it to a higher velocity that gave better performance as far as wind drift was concerned. The trade off of these 52 grain, 3,250ish loads was that the barrel copper fouled to the point that groups started to open up slightly after 20 rounds, nothing that you would notice in the field, but I was punching paper. While playing around with different loads, I found that there was another accuracy sweet spot at around 3,000 or slightly less, that was just as accurate, but with more wind drift, but almost no jacket fouling. From that experience I learned that particularly for factory barrels that are less than totally smooth, the occurrence of jacket fouling is closely related to velocity. I think that this plays to the advantage of .308 heavy bullet loads.
The other issue with the duce, and other factory barrels is that if you clean them to a spotless, condition, it usually takes several rounds for their bores to foul to the point where peak accuracy returns. It was this having to clean relatively often, and having to foul the barrel a number of shots that convinced me to buy my first lapped match grade barrel, a Hart, which was given a tight necked .222 chamber, and from that point, it was a whole new world. If you like to reload, and shoot small, life is too short to waste your time with crappy barrels. My advice is to sell the number of mediocre rifles necessary to finance one excellent rifle. You won't believe the difference, and how much better shooter you are, than you thought you were.
Kevin,
What issue of PS was your cryo test published in. It is the best test, of its type, that has ever been, or is likely to be done.
Boyd
The other issue with the duce, and other factory barrels is that if you clean them to a spotless, condition, it usually takes several rounds for their bores to foul to the point where peak accuracy returns. It was this having to clean relatively often, and having to foul the barrel a number of shots that convinced me to buy my first lapped match grade barrel, a Hart, which was given a tight necked .222 chamber, and from that point, it was a whole new world. If you like to reload, and shoot small, life is too short to waste your time with crappy barrels. My advice is to sell the number of mediocre rifles necessary to finance one excellent rifle. You won't believe the difference, and how much better shooter you are, than you thought you were.
Kevin,
What issue of PS was your cryo test published in. It is the best test, of its type, that has ever been, or is likely to be done.
Boyd
BoydAllen
Gold $$ Contributor
Lapping a barrel that has already been chambered and fitted is not for the average shooter or even gunsmith.
I know a fellow who has learned to do this for himself, but he is exceptional, and he used up one barrel learning how. He went the whole route, and cast a lead lap. One thing that I told him, that helped, that a lot of others may not know, is that you can get a barrel too smooth, and that this can cause jacket fouling problems. I told him that I had heard that a well known barrel manufacturer finish laps with 320 grit aluminum oxide. On that first barrel, he did quite a bit of experimentation, and it turned out that although he was using regular lapping compound of that grit, that that grit size (rather coarse) gave the best results. Later on when he ordered a barrel from one of the most popular cut rifle barrel makers, he looked it over with his bore scope, and found that the interior finish was consistent with what he had gotten with 320. The barrel broke in rather rapidly, and is giving excellent accuracy, in a big magnum, without jacket fouling.
A couple of important things that he did with his process was to slug the barrel before he started, and to monitor his progress during lapping. He also took pains to not have the lap come in and out at the muzzle, doing short strokes of decreasing numbers as he approached the muzzle, without much work there. Of course, keeping the rod centered in the bore, by using adequate guiding means is very important, especially when using such aggressive material. Otherwise it would be quite easy to wipe out the throat of the barrel. This has been done when using abrasives that were designed for cleaning, by getting in too big of a hurry, using sloppy rod technique, and an inadequate bore guide.
I know a fellow who has learned to do this for himself, but he is exceptional, and he used up one barrel learning how. He went the whole route, and cast a lead lap. One thing that I told him, that helped, that a lot of others may not know, is that you can get a barrel too smooth, and that this can cause jacket fouling problems. I told him that I had heard that a well known barrel manufacturer finish laps with 320 grit aluminum oxide. On that first barrel, he did quite a bit of experimentation, and it turned out that although he was using regular lapping compound of that grit, that that grit size (rather coarse) gave the best results. Later on when he ordered a barrel from one of the most popular cut rifle barrel makers, he looked it over with his bore scope, and found that the interior finish was consistent with what he had gotten with 320. The barrel broke in rather rapidly, and is giving excellent accuracy, in a big magnum, without jacket fouling.
A couple of important things that he did with his process was to slug the barrel before he started, and to monitor his progress during lapping. He also took pains to not have the lap come in and out at the muzzle, doing short strokes of decreasing numbers as he approached the muzzle, without much work there. Of course, keeping the rod centered in the bore, by using adequate guiding means is very important, especially when using such aggressive material. Otherwise it would be quite easy to wipe out the throat of the barrel. This has been done when using abrasives that were designed for cleaning, by getting in too big of a hurry, using sloppy rod technique, and an inadequate bore guide.
WyleWD
Silver $$ Contributor
BoydAllen said:
Boyd... a follow up question. Based on your experience and if I understood your post correctly..... if a fellow was giving advice that "you should lap your factory barrel when it is new, and approximately every hundred rounds or less thereafter"..... you'd consider that as ill advised? He went on to tell how that "all" of the benchrest guys paste their barrels almost everytime they clean them.
I've been shooting in a few competitions for around 12 years now and that is the first time I ever heard that. Thanks in advance. WD
BoydAllen
Gold $$ Contributor
I would ask the fellow where he has been shooting. I have attended matches at the Visalia, CA, range (where a number of world record holders are among the competitors) for a number of years both as a spectator, and competitor, and I have not seen that. I should also mention that some shooters may use a little JB or IOSSO on a patch, but that would hardly qualify as any form of lapping, and I have not seen much use of cleaning with abrasives. The most common powder in use in short range benchrest, 133, is very clean at high pressures, and I have been able to pass thorough bore scope inspections with no sign of carbon or jacket fouling, after using very normal cleaning procedures with Butch's, patches, and bronze brushes. Lapping is a specific operation that in the case of barrels is always best left to the manufacturer. Quality barrels only require chambering and very little break in. I may use a little JB on a patch if I have experimented another powder. Carefully done, I think that this is a good thing, in moderation, but in the hands of the ham fisted, and careless, cleaning abrasives can ruin a barrel's throat. If you are going to use these products on an accurate rifle, keep you rod aligned with the bore, AND get rid of that cheap guide, that does not have a bushing on the rod.
Well...you did ask ;-)
Well...you did ask ;-)
Boyd,
Many thanks for the kind words regarding the article. I wish I could tell you, but I don't believe I still have a copy of that one any longer. Sorry, but off the top of my head, I don't recall the issue. Might check with Dave, as it's amazing some of the back issues they have stored away somewhere.
Many thanks for the kind words regarding the article. I wish I could tell you, but I don't believe I still have a copy of that one any longer. Sorry, but off the top of my head, I don't recall the issue. Might check with Dave, as it's amazing some of the back issues they have stored away somewhere.
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