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Wad Substitution - Big Pressure Differences?

Discussion in 'Shooting Related Threads' started by dannyw68, Sep 1, 2009.

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  1. dannyw68

    dannyw68 Member

    Joined:
    Jan 25, 2009
    Messages:
    121
    Hello everyone,

    I just recently switched from claybuster wads (CB1100-12) to Downrange XL1 green wads. I got a great deal on the them and the downrange website says that they can be substituted for for the CB1100-12 and the WAA12SL wads. I use 17 gr of e3 in an STS hull with a Remington 209P primer and 1 oz shot. Although these wads are both supposed to be acceptable substitutes for the WAA12SL wad, the load data from Alliant's website paints a different picture. It states that:

    STS Hull, Rem 209P, 16.5 gr e3, WAA12SL, 10,015 PSI, 1,200 ft/s
    vs.
    STS Hull, Rem 209P, 16.0 gr e3, CB 1100-12, 7,730 PSI, 1,150 ft/s
    STS Hull, Rem 209P, 17.0 gr e3, CB 1100-12, 8,730 PSI, 1,200 ft/s

    Although there is no data point for 16.5 gr e3 with the CB1100-12, you can assume it would be midway between 16 and 17 gr, or about 8,230 PSI. This means that there is a difference of 1785 PSI by switching between wads that are supposed to be interchangeable!

    Does this seem right? Has anyone else encountered this with different component configurations?
     
  2. Paladin

    Paladin Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    4,398
    Contact Downrange. They have pressure test equipment, and may have info on your very question. Wonderful people and product.
     
  3. flybyknight

    flybyknight Member

    Joined:
    Jan 29, 1998
    Messages:
    128
    You have another problem: pressure isn't linear with powder loading - it's exponential. Never assume pressures or velocities, although you would be safe in assumming both the pressure and velocity would be lower than stated if you use less powder. Bob K
     
  4. Quack Shot

    Quack Shot Active Member

    Joined:
    Mar 14, 2006
    Messages:
    4,003
    If the data was compiled on different days and with different lots of primers, powders, etc, then there very well could be some variation. If making substitutions, start with a light load (8000 PSI or so) and hope for the best. There are many variables that can cause discrepancies in pressure between tests. Some powders react to different wads and hulls more dramatically. Some powders are more sensitive to primer variations. Unless you have your own test facilities and an engineering degree, it's difficult to sort it out. I usually recommend that people try to work toward moderately low pressures and hope that's what they get. You could always send some shells out for pressure testing if you need to know. Many wad substitutions appear to develop differences of less than 1000 PSI, but if you are already up against the upper limits it could put you over the top. Start low and stay low.
     
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can i use a cb1100 12 wad in place of waa12sl