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What makes a Rifle accurate?

Discussion in 'Rifle Country' started by Zerstoerer, Feb 21, 2006.

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  1. Zerstoerer

    Zerstoerer Member

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    Gentlemen,
    An invitation to a philosophical discussion:

    What make a rifle accurate?
    How can a company like Tikka promise a 1” group at 100 yards right out of the box, and Weatherby with the Vanguard a group of 1.5 inches?
    Both for rifles in the $500-$600 price range.

    Or, how can other manufacturers like Ruger, Winchester and Remington NOT offer a similar guarantee?
    If you go through the effort of making a rifle why not making sure it will actually be able to hit something?
    Is it all up to tolerances and CNC machining or quality control or what?

    Thank you for your thoughts.
     
  2. Freelance Tax Collector

    Freelance Tax Collector Member

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    Consistency.

    Both on the part of the shooter and the rifle.

    Consistency.
     
    Last edited: Feb 22, 2006
  3. Srigs

    Srigs Member

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    The shooter then the rifle! Train yourself before buying a better rifle. :cool:
     
  4. 50 Shooter

    50 Shooter member

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    Lawyers.:p
     
  5. Cosmoline

    Cosmoline Member

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    A better question might be what makes a rifle INaccurate. In its purest form, on paper, a rifle is at its most accurate. As soon as you start including stocks, slings, screws, shooters, sights, sockets, magazines, actions, receivers, etc. and try to put them all together using imperfect machines and imperfect workers and fire them in an imperfect world the little variations add up.
     
  6. swingset

    swingset Member

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    If you're not sure what makes a rifle accurate, why not study up on the physics of firearms rather than asking a question about manufacturers and their guarantees? The two have nothing to do with each other.

    Accuracy is a recipe. Quality steel, barrel, design, construction, execution, chamber concentricity, caliber, trigger, sights, ammunition, conditions and lastly shooter.

    An accurate gun has the recipe right, the innacurate gun has it wrong somewhere.
     
  7. Zerstoerer

    Zerstoerer Member

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    Don't get excited swingset. I wonder how one manufacturer can get the 'recipe' right and others don't. Do they not know or care if their products perform or do they think it does not matter because the customer will not question it?
     
  8. IV Troop

    IV Troop Member

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    Damn, That was going to be my EXACT answer.
     
  9. colt.45

    colt.45 Member

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  10. swingset

    swingset Member

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  11. USMCRotrHed

    USMCRotrHed Member

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    what makes a rifle accurate

    Barrel
    Bullets
    Bedding

    all these lead to consistency. Every movement must be repeatable.
     
  12. CodeSlinger

    CodeSlinger Member

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    This was also the first thing that crossed my mind, but I've been wondering about something for a while now... What about a dinged crown?

    Many (if not all) accuracy gurus proclaim the importance of an unblemished crown, and many have stories of that one stubborn rifle that just wouldn't shoot decent groups until the dinged crown was recut. It's hard to argue with that kind of empirical evidence, and I don't intend to.

    But I can guarantee you that that ding isn't moving around from shot to shot. That ding is consistent. Yes, a ding causes an uneven force on the bullet when the bullet exits the muzzle, but I would think it'd have to be a consistently uneven force on every shot.

    Thus, I would expect a ding to change POI, but not affect accuracy.

    So what gives? What am I missing?
     
  13. USMCRotrHed

    USMCRotrHed Member

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    Here's the way I understand it...

    The ding in the crown causes unever pressure in the bullet leaving the muzzle and this causes the bullet to tumble around its "yaw" axis. Kind of like a knuckle ball pitch in baseball. This yaw may be less if you can guarantee the pressures in the barrel are always the same, which means you have to use the expensive ammo, or very carefully reload each round exactly the same if you are a reloader. But even then some of the pressures will be off just a little and this will cause the bullet to yaw left or right and up or down and all that varies each time the distance varies. Then you have to consider that the wear around the muzzle erodes differently over time around the nick where it would be a uniform wear if the muzzle was undamaged.
     
  14. redneck2

    redneck2 Member

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    go over to http://www.24hourcampfire.com. John Barsness has a rather extensive article that will answer your question

    In brief...straight and relatively tight chamber. Ammo seated straight. Consistent bullets. These assume no over-riding external factors

    There are external factors like barrel crown, bedding.

    The AR is a perfect example of a rifle that should never shoot well, but can get sub 1/2" groups with just a good barrel and good ammo
     
  15. Rem700SD

    Rem700SD Member

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    I don't own a weatherby, so I don't wan to criticize them. That said, Here's my speculation...

    I'd check to see if weatherby free-floats it's barrels. Secondly, I'd wager weatherbys, at least the magnums, have more "free bore" than a traditional maker. Free bore is the range is the distance the rifle travels before it hits the lands and grooves of the bbl.

    Just something to consider.


    A note on accuracy and it's trade offs. The most accurate rifle on the planet is worthless if it's not right there in shooting condition when you need it. I'd sacrifice that .5 moa to have a go anywhere, do anything rifle within 300 yds.
     
  16. pcf

    pcf Member

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    It's been a while since I've found a factory Winchester, Ruger, Savage, or Remington, that won't shoot sub 1.5" groups, with factory ammo. (Most will shoot sub MOA with factory ammo)

    I'll bet you dollars to donuts that if your factory rifle isn't shooting 2MOA off the bench, with factory ammo, it's the shooter, or something that the shooter did to the rifle that's causing the problem.

    Biggest things that affects a rifles accuracy:
    -The shooter. Sight picture, breath control, trigger control.
    -Shoot off a solid bench and solid chair/stool.
    -Have a good rest for the forend and stock. (old shot bags half filled with sand, and a rolled up towel are not the best choice)
    -A clean barrel and chamber. Oil, grease, dirt, and rust do not belong in your barrel when shooting (the latter never belongs in your barrel).
    -Not damaging the rifle when cleaning.
    -Quality sights and scope that are properly mounted on the rifle, and properly positioned for the shooter. The shooter should be able to naturally mount the rifle and not adjust his head to look through the sights.
    -Properly clean and store rifles after shooting.
     
  17. Essex County

    Essex County Member

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    to reduce it to basics I believe....Barrel, trigger and sights. In that order.. Essex
     
  18. CodeSlinger

    CodeSlinger Member

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    Let me restate that to make sure Im reading the same thing you're saying. ;)

    You're saying that if the ammo was consistent enough, to the point where the excess gas released at the muzzle was the same every round, then my prediction would be correct, i.e. shifted poi but still accurate? It's just that ammo can't realistically be that consistent, and a good crown allows a bullet to be unaffected by the variance in ammo?

    Put another way: A dinged crown does not harm accuracy, but it magnifies the effects of inconsistent ammo.

    That about right?
     
  19. redneck2

    redneck2 Member

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    You guys are missing the whole point

    a solid bench or good trigger doesn't make a rifle accurate, it makes it easier to shoot accurately

    the answer: good barrel (with good bolt lock-up) and good chamber

    excellent bullets seated straight with the proper amount of the right powder

    read the article I referred to, and look at the stuff guys do with factory rifles to shoot benchrest
     
  20. swingset

    swingset Member

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    good barrel doesn't matter if it's not bedded properly, or is the wrong length for the twist (harmonics), or is chambered in a round that's not inherently accurate, or if it's so thin as to wander after 3 shots. Also, bullets no matter how good they are must match the gun's performance, if you shoot a 75gr .224 pill out of a 1/14" twist, it's not going to be accurate.

    I go back to my answer - which is "recipe". A good recipe makes accuracy, all the little things, working together, make a rifle accurate. Quality barrel, caliber, action, bedding, loading, prep and consistency.
     
  21. blackhawk2000

    blackhawk2000 member

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    If you could roll dice the same exact way every time, you would roll the same exact thing every time. It all boils down to repeatability. To roll the dice, you need to hold it exactly the same way every time. Down to the electron width. Same exact throw. Same exact temp. Same wind currents. Same exact velocity, etc. You throw in things like slightly different powder charges, diff wind, diff bolt lockup. As ever slight as these differences may be, POI changes between shots.


    Like said above by others: consistancy
     
  22. JohnKSa

    JohnKSa Member

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    WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.

    Here's my understanding about crowns and why they're important.

    When the gas escapes behind and around the bullet, if everything is smooth and there are no dings, it escapes evenly and consistently.

    When there are dings or irregularities (on the base of the bullet OR the muzzle) then the gas escape forms eddies around the dings and irregularities.

    Those eddies will not be consistent from shot to shot because they are chaotic. Chaotic in the sense that they are mathematically deterministic but yet still not predictable. Chaos in mathematical terms means that while the behavior can be mathematically defined and studied, infinitesimal changes in initial conditions (and I truly mean INFINITESIMAL) cause totally different behavior. Chaos was "discovered" (sort of) when a researcher noted that his computer simulation (using quite simple equations) gave completely different results even though his inputs were the same from one run to the next. It turned out that the very tiny round-off errors in the computer were enough to totally change the behavior of the simulation.

    So the small differences in pressure from shot to shot and the other small changes that can't be eliminated between shots will result in the eddies being VERY different from one shot to the next and may cause large differences in the bullets' behavior from one shot to the next.

    If the escape is over smooth, consistent surfaces that don't promote eddies, then you avoid the "chaotic" case and those small differences from shot to shot cause only small differences in the bullet's behavior. The gases may start to curl and eddy after they get away from the muzzle, but by then the bullet's too far gone to be affected.
     
  23. USMCRotrHed

    USMCRotrHed Member

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    Yes, but that's just my theory


    That would be one way of looking at it. BUT what I was trying to say was that a dinged crown does affect accuracy, but if you have very consistant ammo, the accuracy would be affected in a predictable way each time. However, and inconsistancy would throw the predictability out the window.
     
  24. JohnKSa

    JohnKSa Member

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    WARNING! BEFORE reading farther, please read the disclaimer at the end of the post.
    Yes, but only if it were EXACTLY the same. Not close. Not infinitesimally close. Not so close that the difference is immeasurable with any known techniques. It would have to be EXACTLY the same--PERFECTLY consistent.

    Which is to say that it is impossible. There is no way to have ammo that consistent. If you're asking if making the ammo MORE consistent will decrease the effect, the answer is 'no'. It doesn't work like that. It would have to be PERFECTLY consistent.
    Only in the strictest, most idealized sense. THEORETICALLY, your statement is correct. In practice, it is TOTALLY impossible to achieve the consistency (ABSOLUTE PERFECTION) required to make a dinged crown a non-issue.
     
  25. USMCRotrHed

    USMCRotrHed Member

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    I agree

    The ammunition would have to be exactly the same. Not a real world situation.

    You did a much better job of explaining what I was trying to say, partly because it sounds like you have studied that subject more than I. Thanks for your explaination.
     
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