Bob338,
My e-mail address is cfuruya_us at yahoo dot com or it's on the top bar of the post when you click on the envelope. Thank you very much. Would you like the Audette Load Development article attached on the return?
I'll read your most recent post a little more closely shortly.

Green 788,
I don't agree that runout becomes more important in a hunting rifle type chamber/barrel than it is in a benchrest gun or rail gun. There are too many other sources of error present in a hunting rifle for the concentricity of a round to show it's effect. In short it's masked.

Harold Vaughn addressed this nicely in his book "Rifle Accuracy Facts".

quote:

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We need to talk about the statistics involved in testing. Most people think that if you have a ballistic system (i.e. rifle) that has two error sources and you eliminate one of the errors, the resulting dispersion will be reduced by the amoun of the eliminated error. Unfortunately it doesn't work that way, and depending on the number of error sources in the system, the resulting dispersion will ususally be reduced by a much smaller amount. The reason for this is that the total dispersion of a system is equal to the square root of the sum of the squares of the individual error sources.

---

Best I can express it is;
Total Error = (A^2 +B^2 +C^2...)^1/2
Where A, B, C etc are individual sources of error.

Vaughn plugged in some numbers as an example. He assumed 6 error sources each with an error of 0.6 inches for a total error of 1.47". Removing the first error source reduced group size to 1.34, then 1.20, then 1.04, .85, .60 then 0.

There are probably many more than 6 error sources in the average rifle, and not all providing 0.6 inches each (some probably more and some less).

Thus you can see, removing the first few error sources in a system where there are many has little effect.

For those that have stuck with the discussion this far, I highly recommend Vaughn's book "Rifle Accuracy Facts". Green 788, in it he takes a Rem 721 in 270 Win and examines it's sources of error, explains them, then works to minimizes those error, demonstrating the effects on target. He also comes up with some very novel methods of isolating variables.
He experiences as a supervisor in the Aeroballistics Division of Sandia National Laboratories prove valuable in this book.

[ 01-30-2003, 21:57: Message edited by: Chris F ]

Thanks for the recommendation, Chris.

I suppose for now, Bob338 and I will simply have to dissent, based on our own experiences. Right Bob?

I do understand what Vaughn is saying with the cumulative error factors, but I believe--correct me if I'm wrong--that he is addressing seperate error factors in that thesis.

Reducing the amount of one error factor (such as runout, whether introduced by the cartridge, the chamber or the sum of both) would move us in the direction of better accuracy--or so it would seem. However, the advantage of straight ammunition would likely be totally eclipsed by the negative effect of poor bedding, bolt squaring issues, etc.

I think I'm with you there.

When you mention hunting rifles, I agree that if they are untouched out-of-the-box stockers, you may not be able to see the end result of tuning one error factor at a time, due to the overwhelming assault on accuracy of all the other issues (bad bedding, poor sighting system, bolt lug issues, etc.) combined.

However...

My "hunting" rifles are all glass bedded, mostly free floated, and I make sure the bolt lugs engage correctly, and that the sighting system is in good working order.

I would imagine that Bob 338's rifles are similarly configured, and perhaps that is why he and I are seeing the advantage of reducing runout.

Dan

I swore I wasn't going to post to this thread any longer. I won't after this post.

First, I don't disagree with ANYONE posting their experiences. To disagree with the experiences posted is blatantly calling someone a liar. My disagreement is with faulted CONCLUSIONS. ParticularLY when reached as a result of experiences that are neither validated, controlled, nor with ALL factors considered. Those conclusions should be based on statiscally meaningful numbers. To jump from A to Z without considering the stops in between, or to base them on a half dozen or so events, misleads new or inexperienced shooters who might be swayed by the rhetoric of the writer.

For the benefit of whatever few readers haven't been bored to tears, back to the issue of concentricity. Runout for our purposes is ANY factor which moves ANY portion of the cartridge in the chamber away from the centerline of the bore. It does little to set the bullets to zero runout if the brass fits sloppily in the chamber. If clearances of the brass allows gravity to pull the cartridge away from that bore centerline, runout is being introduce and the zero runout of the seated bullet is meaningless.

Similarly, as mentioned earlier by Chris, the ejectors in the bolt face can cant the cartridge in the chamber if there is any clearance whatsoever. Eccentric chambers, even if minimally eccentric, also can affect concentricity. There are other things, including bolt faces not square with the centerline, crooked brass, and on and on. All we can hope to do is minimize the factors we CAN control in reloading, and there are many. As stated earlier, not everyone cares, nor does it matter in hunting rifles at conservative ranges. Certainly for woods hunting in the east where shots are 100 yards or less, a 3" gun will get the game. In the West where I hunt, shots at 300 yards and more are common. It matters to me to eliminate as many questions surrounding a shot as is humanly possible. Every rifle I have from .338's on down has a custom chamber with throats cut to the bullets I use. The only factory barrels I use are in 375's and larger calibers, and not all those rifles are glassed or otherwise accurized, beyond load development. Those are DGR's where a couple of inch rifle is plenty adequate for the job at hand.

On the other hand, varmint rifles, particularly prairie dog rifles, need to be very accurate. Those shots go out to 400 yards, or more, and the target is small. Removing as many problems from the accuracy question is important.

When you remove as many issues as possible from the question of concentricity you are much better able to isolate other problems which arise. Concentricity IS important, but obviously not for everyone.

Bob338,
Thank you very much for that copy of the Abatiello article which appears to be a second hand account and review of the work done by G Jacobson of Frankford Arsenal. It was very enlightening and brings me a step closer to what I'm looking for.

In short as Bob338 has been saying all along; for each .001" of tilt yields 0.25moa of dispersion on the target. Notably it only affects up to .004" of tilt (and 1.00" dispersion) after which there is no further dispersion.

My next step is to try to find the Jacobson article in the hope that he shares his methodology and testing protocol. If my suspicions are correct, it will be irrefutable as FA was equiped with Mann fixtures (3" diameter barrels anchored in concrete).

Bob338,
Thanks again. I think I'll be picking up one of TomJones' "holes" to straighten my rounds.

BTW, Green 788,
What Vaughn expressed is that the effect of multiple error sources cannot be expressed as simply the sum of the individual errors. (ie 0.6 + 0.6 + 0.6 + 0.6 + 0.6 + 0.6) and removing one source of error from the system will not reduce the total error (group size) by that the individual error amount. It is more accurately expressed in the equation provided previously.

Further, while I can appreciate the pains you took to ensure your rifles were shooting as best they could, Vaughn took it many steps further. For example, he attempted to evaluate how dispersion was affected by receiver asymmetries such as the magazine cutout, loading ports, and scope mounting holes. He attempted to isolate his system from recoil effects, firing pin vibrations and muzzle blast effects. He mounted an accelerometer on his rifle to measure barrel vibrations and examined the various modes and the effect of his modifications on the barrel vibrations...and all the while he is walking us through his thought processes.

Bob338, "First, I don't disagree with ANYONE posting their experiences. To disagree with the experiences posted is blatantly calling someone a liar."

Completely, 100% agree. I've noticed our resident greenRookie is particularly adept at this. When I quit "directly" responding to him, it was because of this exact reason. I've pretty much decided his totally ridiculous posts will suck in a few, but in the long run, as people gain their own experience, they will quickly realize they were PT Barnumed.

Bob338, "Certainly for woods hunting in the east where shots are 100 yards or less, a 3" gun will get the game. In the West where I hunt, shots at 300 yards and more are common."

Now everyone knows the "South"-East is the home of the Bean Field Rifle. Shots get taken farther out(than immaginable) over here every year. Obviously you have not followed(with great interest) the L-o-n-g Range posts like the MatchKing Thread.

And, everyone also knows the "West" is the home of the rifle that "Won the West", the old M94 in 30-30 and the great 44-40 before it. But, I never really thought of them as real L-o-n-g Range rifles. Any chance you all are using MatchKings in them???

Bob338, "Concentricity IS important, but obviously not for everyone."

Actually, a person could just quit Neck Sizing(which is prone to inducing all the Concentricity problems) and go back to good old Partial-Full Length Resizing like I do, but then it would be tougher for me to win BBQ Suppers from them!

Someone mentioned a quote on another thread which is well worth repeating here: "If you can't explain it in layman's terms, you don't understand it."

Bob here is in the precarious position of having the same experience as I have with regard to runout. I say precarious because I apparently bother him , but nonetheless he and I agree that the effects of runout on well tuned "hunting type" rifles can be seen. Right Bob?

Chris, I fully understand Vaughn's thesis, and the reason it is true. Harkening back to the opening line of this post, let me synopsize it this way: If there are a five different imperfections that all collectively contribute to poor accuracy, you can't simply eliminate one of the five and see a 20 percent improvement in accuracy--even if they all contribute equally. So long as there is even one egregious error in the system, accuracy will suffer.

However, at some point along the continuum of reducing error factors you reach the point where bullet runout is important. Here is an interesting link, written coincidentially by Harold Vaughn. We have linked this page and discussed it at length at www.snipershide.com in months past. http://home.snafu.de/l.moeller/Geschosse/Bullet_Imbalance.html

Here, Vaughn drills holes in the sides of bullets to measure the effects of bullet imbalance, and opines later in the piece that jacket imperfections contrubute to imbalace. Perhaps we'll agree that a bullet that gets slammed into the throat of a rifle off center is likely to have some jacket imperfections.

I still think it is very necessary that we differentiate between types of runout, as I mention in the "Types of bullet runout" thread. Even in some of the better written and executed pieces I've read regarding the effects of runout, the very important issue of runout type seems to be ignored. That factor alone would negate the credibility of the results.

Lastly... Hotcore, it's against my good nature to be rude, but you're out of your league here. Chris, Bob, and I have had a spirited discussion so far, and though it doesn't seem likely at this point that any of us are going to back away from any already held positions, we've been reasonably cordial about it. Onlookers to the thread can decide for themselves whose position to believe, (if they believe any of us at all!)But you've added nothing of value to this discussion, and have relegated yourself to a James Carville type, ranting and distracting, missing points, and failing to understand. This isn't to say that you don't have strengths--I believe that you do. Seek out your strong points (again, I've seen them and I know you have them), refine those points and share them with the rest of us.

Good day, gentlemen... And you too, Hotcore!

Dan

Green 788,
With that sampling of Vaughn's book, I'd think you'd have picked it up long ago.

You'd see that he disputes some of the commonly held dogma in Accuracy Shooting and backs it up.

Incidentally, one of the posters on that Sniper's hide made issue of his assertion that Moly increases barrel life. He felt that it was a forgone conclusion given the experiences of the many that it did extend accurate life.

Here's an excellent example of a carefully controlled trial disputing Mass Anecdotal reports. Kevin Thomas of Sierra Bullets wrote of their experiences with identical test barrels. Moly showed no such benefit in their carefully controlled and documented testing.

Chris,

Perhaps we're interpreting Vaughn's assertions in a different way? Or just slightly failing to communicate...

It seems to me that he claims that concentricity affects accuracy, and he demonstrates this with the drilled bullets. If there is a question to debate, it would be "Does excessive bullet runout (bullet canted in the case neck) contribute to jacket deformation, and if so, to what degree?" It would be a given that a significant amount of jacket deformation would affect the bullet's concentricity.

In a properly set up sporter rifle (actually the .270 Vaughn used was a sporter barreled rifle if I read it correctly) the advantages of keeping runout to a minimum should be obvious. I agree if there are egregious problems with the rifle's integrity to begin with, these issues would need to be addressed ahead of realizing any differences between high runout and no runout.

I don't agree that all factory rifles will have such shortcomings, or even that all are typical of the one Vaughn used in his test. (Actually, it is very likely that he sought out a "test" rifle with most or all of these character flaws for purposes of demonstration--not at all a bad idea). But one needs only to observe the incredible accuracy of the average Savage heavy barreled factory rifle to know that these factory rifles are a cut above the hoard. I routinely note the effects of runout in my 100 yard groups--this when it exceeds about .005".

And as Bob338 notes, indexing the runout has a direct effect on the POI. Highpower shooters have done this very thing for eons, and have noted the advantages of doing such.

You mention the moly coated bullet issue, and its relation to barrel life. I'm totally in your camp on this issue.

Curiously, there is a review of Vaugh's work at the bottom of the linked page, where Duncan MacPhereson critiques Vaughn's unwillingness to sign on to the "moly extends bore life" bandwagon.

Here, MacPhereson is probably too hasty in his criticism--in lieu of the excellent study you mention by Sierra's Kevin Thomas. This was written up in one of Precision Shooting's summer or fall issues in 1998, I believe. Kevin did indeed prove with various barrels shooting various types of moly coated bullets (coated by the respective makers of the moly being tested) that barrel life difference was not even measurable. I was particularly interested in these findings because I don't really like fooling with moly coatings. (By the way, I can almost guess who that was at SH that was harping about the extended bore life! )...

Just because the negative impact of a variable is difficult to accurately measure, that wouldn't be (in my mind) evidence that said variable is inconsequential. We correct these issues one at a time--even as Vaugh suggests--in the quest for the most accuracy our rifles can deliver.

Take care, and be well...

Dan

Just realize that the cost of the gauge is just the beginning. What it will teach you will cost you plenty. But the end result is your rifles will start to shoot better.