Switching powders--pressure question

Discussion in 'Reloading' started by BML, Jul 23, 2012.

  1. BML

    BML Well-Known Member

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    Quick question regarding pressures.

    Shooting a 6.5x284. I've been working with H4831SC for load development and now I'm going to switch to H4350

    Published max load for the 4831SC is 45.9
    Published max load for the 4350 is 45.5

    Assuming all else is equal am I safe to just use my current test data and simply drop all the charges I already tested with the 4831SC by .4 grains?
     
  2. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    Not if you haven't shot it at lower charges first. I'd drop down for at least a couple of test groups at ascending charges before you get to max. load again.
     

  3. BML

    BML Well-Known Member

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    I haven't shot it at all yet.

    My max load with the 4831sc is just under 51.0 grains.

    I was planning on starting around 48.5 grains with the H4350.
     
  4. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    Huh???
    You just said in the first post that the published max is 45.9 gr for h4831 sc and you are saying YOUR max is 51. Something doesn't jibe here.
     
  5. BML

    BML Well-Known Member

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    I've never loaded under 48 grains and I don't get any pressure signs at all until 50.8 grains and that was with the bullets .010 into the lands.

    I've never known a published max load to be an actual max load. They are published low to cover their asses from liability issues.
     
  6. BML

    BML Well-Known Member

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    Oh crap I read that wrong. It's 49.5. Damn dislexia kicking in. Glad you said something and made me recheck. That could have been a disaster.
     
  7. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    I've got a few rifles you'll blow your head off with if you try that. My 300 ultra comes to mind; she's doing 3300 fps with a 180 at mid load, and will give bright spots on the brass at top load with many powders. Just because you still get extraction doesn't mean you aren't pushing your luck. I had a strain guage on my last 7stw, and if it seemed warm in that rifle, it was over 65,000 psi already. Some rifles can be pushed a bit if their throat is longer than spec, or the chamber is rather large, but they aren't covering their asses a bit.
    It is naive to think they wouldn't want their bullets going faster than their competitors or their powder producing better speed than the rival companies stuff.
    If you need more speed, get a bigger gun, end of story.
     
  8. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Let's correct an erroneous assumption here; published max loads are exactly that, maximum loads. I can't speak for all companies, but for those I've worked with, those max loads listed are indeed true max pressure loads. We have all too often had customers contact us with what they considered their maximum loads, that have proven to be well into proof load territory. Just because the loads aren't showing what the handloader considers to be pressure signs, doesn't necessarily mean that those loads aren't actually quite warm. Just a word to the wise.
     
  9. rscott5028

    rscott5028 Well-Known Member

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    Why gamble life and limb to avoid backing down/working up with 5-10 rounds?

    Even if it turns out to be a safe load in your rifle, there's no guarantee that max load with one powder will produce the desired accuracy at max load with a different powder.

    -- richard
     
  10. Boss Hoss

    Boss Hoss Well-Known Member

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    I use the H4350 to compete with and 49.5 is the most I have ever loaded with the 142 SMK using a few different tubes. Most of the time settle a little lower than that because it really sucks when shooting a relay in the heat of the day and the bolt gets sticky. Really screws up the bag manners and makes it impossible to win.

    BTW what Kevin said above is the truth... I know that there are a lot of know it all's here but what Kevin said is 100% accurate and if you know his background you will be well advised not to tell him he does not know what he is talking about..