Fast powder vs Slow powder ????

Discussion in 'Reloading' started by Iron Worker, Nov 17, 2008.

  1. Iron Worker

    Iron Worker Well-Known Member

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    22-250AI shooting 80gr Berger VLD 8" twist 26" BBL. H4831 43grs produced avg MV of 3,340 with a couple of cases with shinny ejector marks.... 39grs of IMR 4007 produced avg of 3,365 with no pressure signs. Both produced about same accuracy 1/2 MOA at 100. What is happening in chamber? I thought the slow burners were the ticket when firing heavy bullets....
     
  2. eddybo

    eddybo Well-Known Member

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    IronWorker,

    I havent looked on a burn rate chart, but didnt think there was that much difference between thos two to make much of a difference....have you tried any VV560 or RL22? I do not load for the 22-250 but do a good bit of reloading for a 22-6.5x47 lapua which has about the same capacity.

    I think that all of the traditional pressure signs that people see are from the initial shock of the bullet leaving the case and engaging the lands which creates a pressure spike which dissapates as the projectile proceeds down the barrel thus creating a larger pressure vessel.
     

  3. uncleB

    uncleB Well-Known Member

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    Iron Worker,
    You show muzzle velocities of the two loads but how about the SD numbers. IMR4007ssc is in the same burn rate as H380 that would be a great powder for 50grain bullets but for 80's I am guessing the SD is high.
    If your rifle does not like H4831 tinker with other powders in the appropriate burn rate like IMR4831 on the fast side and N165 ,RL22 and IMR7828 on the slow side and when chronographing try and find a load that has good muzzle velocity and single digit SD numbers.
    Your most consistent load with good muzzle velocity is 1000 times better than the fastest load with a SD of 50.
    UB
     
  4. Iron Worker

    Iron Worker Well-Known Member

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    Out of 5 rnds 3,341 3,333 3,345 3,345,3,362 3,347 Main thing is there were no apparent pressure signs with the fast burner. I tried RE#22 the SD was 50 FPS between 3 shots. Thanks
     
  5. 308sako

    308sako Well-Known Member

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    As the caliber diminishes the need for a relatively faster powder for best accuracy increases. Just because a powder will fit into a case that does not make it the best choice. I've been loading the .22/250 since 1966 and (of course lighter bullets) but the powder then was the H380 or IMR 4064. IMR 3031 gave excellent velocity and accuracy as well (52 grain bullets) The magnum mind we have all adapted to calls out for us to use the charcoal, but the powder fouling and in accuracy issues plague us. Then there is the cartridge case issues which make some propellants more desirable than others, heck the 6.5/284 loves the H4350, so would you consider that a fast or slow powder?
     
  6. Iron Worker

    Iron Worker Well-Known Member

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    H4350 is a medium slow burner,burns slower then what you listed but faster then H4831 and we know there a many many slower burning powders then H4831.
     
  7. milo-2

    milo-2 Well-Known Member

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    +1 on what this guy said.
    I run 75gr Berger, 42.0gr of N560, 3400 fps.
     
  8. Loner

    Loner Well-Known Member

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    A slow burning powder can cause a secondary pressure spike that is much higher than
    the primary. A lab won't even tell you it occured unless you ask them to include it in
    the results. The theory is; As the bullet gets a little way into the barrel the powder burn
    rate accelerates rapidly due to heat and more case capacity, It catches the bullet as it
    slows from the initial burn having not burned all the powder. These spikes have produced
    pressures in excess of 150,00 psi and are pretty much ignored (or not talked about) by the shooting industry at large. A faster powder is the way to avoid them. Also your throat
    will live longer if more powder is burnt in the case instead of the barrel.