Home Forums Hunting & Shooting Ask The Gunwriters What causes accuracy?

RobP,

A couple of comments on your excellent post:

I did considerable bullet experimenting with a Juenke Internal Concentricity Comparator a few years ago. The ICC uses ultra-sound on a rolling bullet to measure how well the bullet is balanced, which has a LOT to do with accuracy. The machine absolutely predicted which bullets would tend to shoot better in any batch.

Once I proved how well the machine work, I tried measuring and weighing bullets to see if either technique could also pick out the "bad" bullets, instead of using a $700 machine. There wasn't any correlation. In fact, the bullets rated as most concentric by the Juenke machine (and shot very well) usually varied by a few tenths of a grain in weight, or had slight differences in diameter. My conclusion was that measuring or weighing bullets is pretty much a waste of time.

Unfortunately, the machine was on loan for a year and had to be returned. Since then Vern Juenke retired and no longer makes them. The only way to "sort" for accurate bullets I've found since then is to buy bullets with a reputation for accuracy--and even then, as you point out, even the best bullets will vary from lot to lot.

Your comments about dies are spot-on. Many handloaders have no clue about how good or bad their dies are, and without good dies you can't make good ammo. However, it isn't absllutely necessary to use hand dies. I have a 6mm PPC benchrest rifle and load the ammo on a Redding T7 turret press in Redding Competition dies. That combo produces rounds with no more than .00005 bullet run-out, and with the right loads the rifle averages 5 shots in the .1's at 100 yards.

I think that to answer the OP's original queastion, it comes down to barrel harmonics. All barrels are in essence, tuning forks. Just a little different vibration can send bullets in different directions. Or you can look at it like your garden hose spray nozzle. Just a little more or less pressure and water goes out in a wide pattern. But hit that sweet spot, and its one long solid column of water.

This is as good an answer as any other.

I used to think it was witchcraft, now I'm pretty sure it's voodoo........



Casey

I generally don't like smartazzes who pick apart words, etc.

But, technically speaking, precision and accuracy aren't exactly the same, although used fairly interchangeably in many writings. And we all know what the writer means.

"Precision" is the group size and repeatablity of that performance.

"Accuracy" is putting the bullet where it needs to go, "gun control" in the best sense of the term.

Nit picking...

DF

mathman thanks you!

That was my first inclination, too. Many of the things mentioned in a couple of detailed excellent posts here, more or less affect barrel vibrations. Handloading, all the other efforts notwithstanding, is about finding that magic formula that generates the most consistent and/or minimal vibration that permits repeatable accuracy.

But it's like everything else in life. If getting a rifle to group one inch takes X amount of time/dollars/practice, getting from there to under half inch groups generally will require exponentially increasing time/effort...and usually money!

Not necessarily.

In my experience, repeatable small groups are hardest to come by in rifles with stuff wrong with them that prevent small groups. That's because the barrel vibrates in various ways, due any number of factors.

In rifles that are put together right, small groups are pretty easy, and not much experimenting is necessary. They'll shoot about any good bullet with about any semi-appropriate powder.

That's why I suggested the Harold Vaughn book earlier in this thread. It's all about what causes accuracy, and it ain't magic or voodoo.

Many great comments.

I would like to add a few that seem to make a difference in what I have personally seen.

A good reamer with dimensions held to the tighter side of SAMMI specs with reduced neck release space and the right throat angle. I recently read that the 308 outshot the 30-06 when it first came out because the original 30-06's used a 2 1/2 degree throat where the 308 used a 1 1/2 degree. The author stated the steeper 30-06 throat angle was hard on the bullets influencing accuracy. Not sure where I read it or I'd link it.

A good crown. A crown that passes inspection with a borescope not one that looks good with the eyes will make a difference.

I agree with the other posters that every accuracy enhancement helps. Bedding, good trigger, quality barrel, good bullets etc.


Naturally every aspect of consistency in handloading plays its part. To answer your question, some powders just work better than others. Some loading books point out the most accurate powder.

Good thread.

One of the reasons I've published lists of "Loads That Work" is because certain loads do tend to work in good rifles of a certain chambering. And part of the reason I try such loads in any new-to-me rifle of that chambering is because if the load doesn't shoot well, then I know there's something wrong with the rifle.

I like accurate firearms as much as the next guy,...but there's a point that I won't allow my obsessive/compulsive nature to cross.

Madness lies on the other side.

Harmonics.

Lots of great information in this thread.

My experience with squeezing out the most from off the shelf mass produced rifles is below. Most have been good but we are at the mercy of the machinest/assemblers for barrel to action fit.

I would throw out for consideration that I do not crimp except for tube magazine rifles for the most part and I load off the Lands for hunting so that if I have to unload a loaded round, I do not pull the bullet and spill powder....

And while others may not agree with this, I find that the distance from ogive to rifling was one of the things that helped get rid of the occasional unexplained flyers. As I load, I measure with Hornady tool and make adjustments with seater die to make that distance to the lands consistent rather than the end to end distance or OAL. Edit Added: Each round is measured individually. I back off the seater and do a preliminary seating and measurement. Pain is the AZZ but so are flyers.

There are so many variables......And then when all else fails there is also witchcraft.

Seating depth is certainly one factor most handloaders don't consider.

But I would reiterate that the reason "harmonics" is usually given as the reason for accuracy is because the average rifle causes erratic harmonics. If we eliminate those problems, then rifles will shoot accurately with a variety of loads.

Maybe one way to calm down harmonics is to full length bed the rifle. It keeps everything as one unit as the barrel and stock become one in peace and harmony.
Jeez, I need more coffee. Sort of what Melvin Forbes theory is.

Accuracy Is a learned skill set of monotonous repetition administered with a firearm and load combination that is repetitious. And so forth. Or what Rob said.

I cause accuracy.



Travis

FINALLY we get the answer....

Despite my arrogance it is true.

Benchrest is akin to Formula 1. Most that equipment is equal, so it comes down to being the best driver on that day, or being the best shooter that day.

And if you get your head to wrapped up in it all, they still sell Budweiser.



Travis

As the resident rattle-shaker, whenever it gets into magic and witchcraft, I am obligated to weigh-in.

First off, forget witchcraft. That's just a bunch of overweight lesbians that like to dress goth. They can't shoot worth a poop.

Magic? Now, there you have something.

Look, I'm not all that great a shooter, and I don't own a true 1/2 MOA rifle. However, DogZapper got the first part of the thing right: a good foundation-- The 4 B's.

However, that is all just prelude. Somehow you have to do on the inside what you've managed to achieve on the outside. The rifle and the load have to be right, but far more importantly you have to be right.

For that, there needs to be a lack of "You" . Practice and repetition go a long way to achieving this, but basically you need to remove yourself from the process.

A good book for discussing this is Zen and the Art of Archery by Eugen Herrigel. It is a basic introduction to Zen. I'm not a big fan of Zen-- I'm much more of a Taoist by nature. You remember Chin, the Chinaman? He's a friend of Pooh. Chin is a first rate Taoist crank. Chin and I were talking one day and I was trying to get out of that old fart how it all works from his point of view.

Chin said, "It is like a monkey catapulting through the jungle:
Totally fascinated by the realm of the senses, it swings from one desire to the next, one conflict to the next, one self-centered idea to the next. If you threaten it, it actually fears for its life.

Let this monkey go.
Let the senses go. Let desires go.
Let conflicts go.
Let ideas go.
Let the fiction of life and death go.
Just remain in the center, watching.

And then forget that you are there."


That pretty much sums it up.