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Pattern density decline with increased velocity??

Discussion in 'Shooting Related Threads' started by Longhorn, Apr 11, 2013.

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  1. Longhorn

    Longhorn Member

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    I have heard from many shooters that patterns disintegrate as velocities increase. I don't see why this can be the case. Have any studies been done regarding this? Are there any "experts" who can offer some information to this ballistics challenged shooter?
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    Try the link above, LH. It's pretty fresh and so has not yet been superseded by newer data.

    Neil
     
  3. Stl Flyn

    Stl Flyn Well-Known Member

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    Here comes an argument in the making. Neil will be along shortly, I am sure. Then the others will try and argue his theory.

    Man this Winter is just dragging, and dragging, and dragging, and dragging, and dragging.....

    Hey, Neil beat me to it.
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    It's not a theory, Jon. It's just the result of testing. Not as good as a theory for TS.com, I agree, but the best I could do.

    Neil
     
  5. W.P.T.

    W.P.T. TS Member

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    The increase in velocity would probably or could possibly cause holes in the pattern that might not be there otherwise ... WPT ... (YAC) ...
     
  6. hmb

    hmb Well-Known Member

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    Buffetting, we are encountering extreme buffetting. From the movie Breaking the Sound Barrier. Passing through the sound barrier will change your pattern. HMB
     
  7. Neil Winston

    Neil Winston Well-Known Member

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    But WPT, as I clearly explained on the other thread, holes are a function of the number of pellets in the pattern, nothing else. And since there is no difference in the number of pellets in the patterns in the range of 1150 to 1300 feet-per-second, there will be no difference in the number of holes.

    Neil
     
  8. W.P.T.

    W.P.T. TS Member

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    Ok Neil, yeah I forgot ... (Making a note right now) ... Respectfully, WPT ... (YAC) ...
     
  9. Tom Strunk

    Tom Strunk Well-Known Member

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    I don't think Leo or Harlan worry about it. They both shoot handicap shells.

    Tom
     
  10. Longhorn

    Longhorn Member

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    Neil, 1st class info. Thanks for making your findings available. Much more reliable than mere theory.
     
  11. Dr.Longshot

    Dr.Longshot Banned Banned

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    How about 1 1/8th oz #6s at 1500fps? Using Longshot 35.3 grs in STS hull using Windjammer wad Winchester Primer @10,000psi 1530fps bet it don't blow the pattern?

    Gary Bryant
    Dr.longshot
     
  12. dale1957

    dale1957 Member

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    Read the most extensive book ever written about shot-gunning. The book is titled " Shotgunning The Art And Science" written by Bob Brister. It is the most in-depth book on this subject. He does say the faster the velocity, the faster it opens-up. But there r many varibles. Check it out.
     
  13. Beretta Young Gun

    Beretta Young Gun Active Member

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    I think pattern of a shell has more to do with pressure than the speed. In reloading the more powder you put in a shell the faster it will go but the pressure also goes up. Using exactly the same components with the exception of powder amount try patterning a shell. 1100FPS VS 1300FPS, Ill bet you will be suprised. Its the pressure that opens a pattern, not the speed. In a new shell such as AA it wouldnt be a fair comparison given that a 3 dram AA uses a different blend of powder than there handicap shells. BYG
     
  14. Neil Winston

    Neil Winston Well-Known Member

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    dale, following your advice to check it out I did. And what I found was about what I remembered.

    "This brings up another long-standing idea of shooters which is partially correct and partially untrue, the contention that adding velocity opens patterns and that reducing velocity tightens them. As a rule of thumb this idea is true. But it not necessarily the the velocity that makes the difference, it is the shot deformation. If shot are sufficiently hard to resist deformation at the higher pressures of high velocity, then they pattern about as well as the same shot at lower velocity. I tested this with the highest velocity loads I have ever put through a gun barrel and the hardest shot of them all - steel." (page 166.)

    It seems to me, Dale, that Bob Brister supports, rather than contradicts, the data I presented above (which was, of course, obtained with hard magnum (STS) shot.)

    That's not the impression I got from your post.

    Neil
     
  15. Dr A C Jones

    Dr A C Jones Member

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    The shot doesn't "see" pressure, it only experiences the effects of forces - acceleration at the start and then compression when passing through the choke.

    I wonder if the small increase in pattern density for very slow loads and no measured (to date) incremental increase at higher levels is due to the compressibility of the shot ensemble. Lead is largely incompressible, but it is deformable. Once it is deformed so that most of the air spaces in the shot column are removed, then further deformation is much more difficult. It might just be that ~1100fps give or take is the threshold above which further deformation is very much harder to effect.

    That's speculative on my part, but it's more plausible than the pressure or subsonic theories.

    Andrew.
     
  16. Neil Winston

    Neil Winston Well-Known Member

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    BYG, your idea is exactly what my 1030, 1130, and 1230 pfs experiment tested.

    Reexamine the third and fifth graphs in the post links to the "Website URL" above.

    What you predict did not happen. Increased speed and pressure were both present and for the most part, it made little (1030 vs 1130 fps) or no difference (1130 vs 1230), the latter where you would, according to your theory, expect the most dramatic effect.

    Really people, if you are dissatisfied with my results it does little good to make up quotes from classic sources or offer contrasting "explanations" for effects that are not, in fact, observed. The counter to inaccurate experiments is better experiments, not typing. There's a difference.

    Neil
     
  17. Dr A C Jones

    Dr A C Jones Member

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    It's actually very hard to isolate the speed versus spread effect. If one does as Neil did with loads at different speeds, it's not just speed that is effected but also, possibly, shot deformation. i.e., the pattern plate shows the result of faster deformed pellets vs slower less deformed ones, which is not speed alone. One could use less shot in the faster load case so that set-back forces are less, but then the pattern test transmogrifies into "fast small cloud versus larger slower cloud", and we don't know what effect shot cloud size. So, it's very hard to isolate the speed element.

    The only way I can think of is to use a giant air shotgun that gently accelerates the shot, thus taking set-back forces out of the equation.

    Andrew.
     
  18. drgondog

    drgondog Member

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    Drag.

    Function of Velocity "squared', combined with semi-spherical (deformed) shot, should tend to move such shot off the centerline of the pattern.

    Theoretically, deformed shot should rotate in comparison to perfectly sperical shot. If so, rotational shot will behave like a curveball and experience a differential pressure distribution tangential to the freestream velocity - and move in the direction of the force.

    In a vacuum it wouldn't matter.

    Take what you want and leave the rest
     
  19. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Should we leave Hevi-Shot out of the discussion? Ugliest shot ever inserted into a shot shell yet it patterns good and retains downrange power beyond belief?

    If we attempt to compare lead and steel, weight of individual spheres and diameter size must also be considered. For a steel pellet to weight the same as say a lead 7-1/2, it must be larger in diameter? Wind drag will be far different as a result on the steel pellets making the comparison not too difficult, especially at longer range.

    The faster you throw a knuckleball, the more movement it has!

    If we use Dr. Andrew's program to measure patterns shot and photographed at a measured 40 yards. One at 1090 and one at 1300 fps, same amount of lead and size. The pattern centers will measure the same for height above the POA but would the PE will change. Why?

    Hap
     
  20. drgondog

    drgondog Member

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    Steel and Hevi Shot are far harder and less susceptible to deformation than lead - implying less 'wandering'.
     
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