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"Rifle Accuracy Facts" by Harold Vaughn

Posted: Sat Oct 31, 2015 5:23 pm
by mtngun
I thought I posted a review of this book a long time ago but maybe not. In any event I re-read the book recently and it came across much better the second time around. :lol:

Vaughn was a retired engineer who took a scientific approach to shooting. It's a nerdy book, so if you have a background in science or engineering you'll enjoy it. :lol: If you're not a nerd then you probably won't get much out of it.

The first time I read it, I was put off by Harold's personal style. He came across as cocky yet didn't present a lot of data to back up his claims -- we just had to take his word for it. For example, I don't think there is a picture of a single target in the entire book.

However, in fairness to Harold it was probably the editor's decision to leave out a lot of the test data. The fact is, boring data does not sell books. Likewise there is very little data in Colonel Harrison's "Cast Bullets" book even though the Colonel claimed he conducted thousands of tests in the course of writing his book. In both cases, the editor probably left out most of the data to make the book more readable. I don't like it, but that's the nature of publishing. :?

The second time I read it, it didn't come across as particularly cocky except in a couple of places. One example is the section on his 6 Degrees of Freedom Exterior Ballistics (6DOF) computer program. He mentions repeatedly that the 6DOF program is the greatest thing since sliced bread, but then never shares the program with the reader. Well, what good does it do us to hear about a computer program that we have no access to? It comes across as showing off -- "hey look at me, I wrote this cool program, but you can't have it, nah na nah nah" :twisted:

That said, I enjoyed the heck out of the book. It made me think. Even when I disagreed with Harold, he still made me think about things that I hadn't thought about before. 8-)

The biggest single part of the book that I question is Vaughn's claim that Spiralock barrel threads and torqueing the hell out of the barrel improved accuracy. I can't argue with his logic or with his data, such as it is, but the bottom line is that lots of benchrest shooters don't use Spiralock threads and don't torque the hell out their barrels and yet it doesn't seem to hurt their accuracy.

I'll highlight a few of the book's points that are particularly relevant to cast bullets. On page 170 he identifies bullet imbalance as a major limitation to accuracy and even gives us a nice equation to quantify it. Since our cast bullets will never be as well balanced as a jacketed bullet, I think that particularly concerns us.
Image

The takeaway is that dispersion due to imbalance increases proportional to velocity -- no wonder it's so hard get high velocity cast to shoot well ! ;) Another important takeaway is that we can minimize the dispersion due to imbalance by using a slower twist.

That's not a new discovery, but Vaughn does a great job of cutting through the myths surrounding RPMs and instead explains it in precise, scientific terms.

Another Vaughn point that is relevant to cast bullets is that bullet friction is much ado about nothing, and that bullet lubes actually reduce velocity to the extent that the lube interacts with the hot gases and cools the gases (p. 231).

All in all I admire the heck out of Harold and wish there were more shooters like him in the world. By the way, the book is out of print and has become a collector's item. Used copies start at $500 and go up to $6000. :o

Re: "Rifle Accuracy Facts" by Harold Vaughn

Posted: Sun Jun 18, 2017 9:56 am
by PG1
Hi,

Your review gave me a new incentive to look for Harold's book in pdf format, since the paper versions are outrageously expensive. I found a scanned version on scribd that is readable but loads slowly because each page is an image. The book is a big inspiration to those of us who like to tinker with rifles and try to understand why they shoot the way they do.

I really enjoyed his approach of instrumenting and measuring his rifles to test ideas instead of relying on guesses and tribal knowledge.
in particular the following stood out for me:
-- strain gage measurement of the bending moment in horizontal, vertical planes and correlation with shot dispersion, together with experimental data on how to make the horizontal moment smaller via symmetry.
-- measurement of the rotational velocity (rpm) of solid and jacketed bullets to estimate the rpm where core stripping occurs. Have never seen this measured anywhere else.
-- accelerometer measurement of muzzle movement and correlation with vibrational modes. Again, the data are unique. There is another measurement of muzzle tilt by border barrels using optical techniques but on a .22 barrel where the forces are lower.

-- Dynamic imbalance measurement of bullets. Although the apparatus looks complex, it may be worth repeating for those interested in super accurate bullets.

I did not find Harold's analysis of the barrel threads to be unsound, although have not yet run the numbers on the stresses. However, he did take the trouble to measure barrel pointing error and correlate that to where the shots landed, so I think his conclusions are justified.

While there are no actual photos of paper targets, there are numerous diagrams showing shot dispersion in various conditions. For me this is more readable because the photos in the book are not all that clear, particularly in the scanned version.

Am still absorbing and analyzing the data presented, this is a data-intensive book and has a lot to offer. But for those without a graduate level engineering background, it may be tough going. Harold Vaughn has a deep knowledge of hydrodynamics and projectile dynamics which shows clearly in his approach and analysis.

Paul

Re: "Rifle Accuracy Facts" by Harold Vaughn

Posted: Sun Jun 18, 2017 9:56 am
by PG1
Hi,

Your review gave me a new incentive to look for Harold's book in pdf format, since the paper versions are outrageously expensive. I found a scanned version on scribd that is readable but loads slowly because each page is an image. The book is a big inspiration to those of us who like to tinker with rifles and try to understand why they shoot the way they do.

I really enjoyed his approach of instrumenting and measuring his rifles to test ideas instead of relying on guesses and tribal knowledge.
in particular the following stood out for me:
-- strain gage measurement of the bending moment in horizontal, vertical planes and correlation with shot dispersion, together with experimental data on how to make the horizontal moment smaller via symmetry.
-- measurement of the rotational velocity (rpm) of solid and jacketed bullets to estimate the rpm where core stripping occurs. Have never seen this measured anywhere else.
-- accelerometer measurement of muzzle movement and correlation with vibrational modes. Again, the data are unique. There is another measurement of muzzle tilt by border barrels using optical techniques but on a .22 barrel where the forces are lower.

-- Dynamic imbalance measurement of bullets. Although the apparatus looks complex, it may be worth repeating for those interested in super accurate bullets.

I did not find Harold's analysis of the barrel threads to be unsound, although have not yet run the numbers on the stresses. However, he did take the trouble to measure barrel pointing error and correlate that to where the shots landed, so I think his conclusions are justified.

While there are no actual photos of paper targets, there are numerous diagrams showing shot dispersion in various conditions. For me this is more readable because the photos in the book are not all that clear, particularly in the scanned version.

Am still absorbing and analyzing the data presented, this is a data-intensive book and has a lot to offer. But for those without a graduate level engineering background, it may be tough going. Harold Vaughn has a deep knowledge of hydrodynamics and projectile dynamics which shows clearly in his approach and analysis.

Paul

Re: "Rifle Accuracy Facts" by Harold Vaughn

Posted: Sun Jun 18, 2017 1:11 pm
by mtngun
If enjoyed Vaughn's book, you might also enjoy Jim Boatwright's site: The Well Guided Bullet.