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WAD EFFECT ON PRESSURE

Discussion in 'Shooting Related Threads' started by tsosin, Aug 12, 2009.

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  1. tsosin

    tsosin TS Member

    Joined:
    Jul 9, 2007
    Messages:
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    For over a year I have been shooting a one oz. load using 17.5 grains of red dot in an STS hull with a green duster wad. That load chronagraphed at 1230 fps. In researching other loads, I've noticed a great deal of difference in recipes using the same the same powder weight but different wads, and the problem is made more difficlt by the fact that not all powder companies list loads for all of the available wads on the market.

    My question is how much difference in pressure is created using a straight wall wad like a green duster(which is listed as a replacement for the WAA12SL) in a tapered wall hull. I would think that the logical answer is that it increases the pressure due to a tighter fit, and increases the fps up to a point, but I'm sure that someone can steer me in the right direction.

    I really like the way dusters load so I'm just looking for one load at about 1145-1160 and another at 1230 to 1250 for handicaps. I found both loads using clays and claydot charts, but I've got a fair amount of red dot to burn before I switch.

    Thank you for any help you can provide.
     
  2. goatskin

    goatskin TS Member

    Joined:
    Jun 24, 2009
    Messages:
    1,781
    The Green Duster is not a 'straight-wall' wad. It is a Win clone, with a tapered over powder cup.

    Yes, some wads are more efficient that others, but the Winchester and clones are not they. You may get a slight increase in velocity with a more efficient wad, but not necessarily.

    Bob
     
  3. halfmile

    halfmile Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    15,642
    Location:
    Green Bay Wisconsin
    The folks at Olin, years ago told me the deal. they were advising me on a problem with Super-Target powder.

    I had been using Windjammer wads, and getting blowby. They analyzed 25 shells I sent them, before and after firing.

    They told me to use a higher pressure wad, the AA Winchester to get a better seal. More conversation revealed that wads that were flat on the bottom,(the side facing the powder) produced less pressure than wads that had a concave bottom.

    It didn't take 2 seconds for me to relate that fact to hemispherical combustion chambers and flame travel in racing engines.

    So there's my take on it, and since then my observations bear it out.

    Concave base, higher pressure.

    Flat base, Lower pressure.

    Some wads like the figure 8 have an in between configuration, and I feel they perform accordingly.

    Incicentally the kind folks at Olin sent me 4 lbs of powder for my trouble.

    HM
     
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