Slow burn vs fast burn powders

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  • Slow burn vs fast burn powders

    I've always just followed convention when choosing a powder for a cartridge, but I was thinking about it the other day. It seems logical to me that slow burning powders would be good for lower velocity cartridges like the Grendel since they are in the barrel longer and would allow longer for the powder to burn and push the bullet, especially when in a long barrel. Reality is the huge cased, super fast magnums are where the really slow burners go. Can someone explain why that is and what I'm missing?

  • #2
    This is what I have found in 35+ years of loading, tho I would add right away that I learn new things all the time:

    The slower the powder in a given cartridge, the more you can put in safely. That said, what you want is as close to 100% loading density as you can be. I have a few recipes that exceed 100%, for a compressed charge. The 6.5 tends to be one of those, as with the slower powders I can fill right to the neck, then compress when seating the bullet.
    Obviously, there is a limit to everything, and you can't just scoop 4831 into the 6.5 and expect good results.
    But, in general, you want the powder(s) that fill the case. I have found H4895 and WW748 to be a couple that have worked well in the 6.5
    There are, to be sure, many more, but in the interest of economy, I found some that also work well in my 5.56, and stopped right there.

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    • LR1955
      Super Moderator
      • Mar 2011
      • 3355

      #3
      Originally posted by z06man View Post
      I've always just followed convention when choosing a powder for a cartridge, but I was thinking about it the other day. It seems logical to me that slow burning powders would be good for lower velocity cartridges like the Grendel since they are in the barrel longer and would allow longer for the powder to burn and push the bullet, especially when in a long barrel. Reality is the huge cased, super fast magnums are where the really slow burners go. Can someone explain why that is and what I'm missing?
      Z6:

      From what I recall from reading on this in the past, you need a-lot of pressure for the slow burning powders to burn and burn efficiently. So, heavier bullets are needed to provide enough pressure for these powders to work with any degree of efficiency. Thus you see them used in oversized cartridges shooting small diameter bullets.

      Take a look at some load data for the 7.62 X 39 and compare the powders used to that of the Grendel, a slightly oversized 7.62 X 39 but shooting a much smaller diameter bullet.

      With the Grendel, a slow powder only gives you much lower velocities. Sure, they work, but they just aren't efficient.

      LR1955

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