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Velocity vs pattern spread

Discussion in 'Shooting Related Threads' started by hmb, Jun 7, 2010.

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  1. hmb

    hmb Well-Known Member

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    You will get a tighter pattern at 1090 fps because it is sub sonic. When the shot string passes through the sound barrier it encounters turbulence which increases the size and lowers the density of the pattern. HMB
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    HMB might be right. Slow pellets did print tighter in an experiment I did. Everything from 1140 to 1290 was the same, though.

    Neil
     
  3. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    I shot 1-1/8 oz at 1090 and 1310 fps at close yardage and the slow load was the tighter grouping patterns. If it's tighter at short yardage, it's tighter farther out also.

    Hap
     
  4. dverna

    dverna Active Member

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    Most .22 target ammo is sub-sonic for a reason - accuracy.

    Here is a quote from a site regarding air gun pellets and speed:

    "As it turns out, .22 long rifle ammunition, which fires a 40-grain lead bullet, is ALSO less accurate if the bullet goes supersonic. Why? Because when it is just barely supersonic, as most .22 LR high-speed ammo is, the bullet gets tossed around by its own sonic wave. To get around this, a bullet has to be extremely streamlined and it needs to be shot at several times the speed of sound. So, if you can get your solid pellets out the muzzle at 1,400 f.p.s. and faster, there may be an advantage. Less than that and you are tossing away accuracy. That's why all .22 rimfire target ammo is subsonic. Learn from the target shooters and stay well under the sound barrier."

    Shotgun velocities are also barely supersonic.

    Don Verna
     
  5. phirel

    phirel TS Member

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    I have never patterned anything slower than 1150 ft/sec. But like Neil, I have not seen a pattern spread (# of holes in the 20 inch circle) due to velocities between 1150 and 1250. I am not sure about "turbulence due to passing the speed of sound". The speed of sound is not a constant. I do not know how to measure the over all size of a pattern. I do know that not all shot are within a 30 inch circle and increased speed could result in the stray shot flying further away from the center.

    Pat Ireland
     
  6. ke4yyd

    ke4yyd Member

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    Many top skeet shooters swear that .410 velocities of 1350 fps or so produce tighter patterns. Remington .410 skeet loads run about 1350 fps and folks that shoot them regularly use less constriction in their chokes to get the same pattern density.
     
  7. markostrunk

    markostrunk Member

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    We should also remember that, all things being equal, the greater the velocity, the greater the initial setback in the shot column at ignition. That means more distortion of the pellets at the back of the column. Distorted pellets fly less true and pattern wider.
     
  8. wayneo

    wayneo Active Member

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    I too have pattered lower velocity loads, and they do seem to be a little tighter....But, if your dropping velocities, your also dropping pressures. Once you go below the powder manufactures recommended pressure, inconsistent, and incomplete powder burn happens and your patterns will not be consistent. You will also be losing pellet energy with lower velocities and pressures, not a good thing for trap. Wayne
     
  9. hmb

    hmb Well-Known Member

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    Those skeet shooters are sneaky devils. Here's what they were doing. Since the shot left the muzzle at 1350, when it got to the target it was still traveling above the speed of sound. The pattern disturbing effects are only encountered when passing through the sound barrier. So as long as their shot charge reached target at about 1120 fps it encountered no tubulence. HMB
     
  10. mx2k33

    mx2k33 Well-Known Member

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    Spheres are very poor projectiles aerodynamically. Very few actually hit the point of aim at distance (hence a "pattern"). Higher velocities cause greater setback pressures and deform lead pellets which in turn encounter higher wind resistance and fly outside the main pattern of less deformed pellets which occupy the core. Steel shot does not deform as readily and therfore requires less choke to achieve tighter patterns (compared to lead)even at higher velocities.
     
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