.300 RUM + 240 SMK loads using US869?

Discussion in 'Reloading' started by yote bomber, Jul 10, 2008.

  1. yote bomber

    yote bomber Well-Known Member

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    Just picked up a pound of US869 and a box of the 240 Sierra Match Kings... I've seen a little bit of data on here for this combo, but most of it seems like it was shot in custom rifles. I'll be running them out of a stock Sendero in .300 RUM...

    I'm thinking starting somwhere in the 93 grain range and working up? I'm thinking 2850 should be an acceptable velocity, as long as the accuracy/consistency are there. Anyone got any suggestions on where the velocity should be?
     
  2. jmatson

    jmatson Active Member

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    My "Quick Load" v3.4 93.0g of US 869 2678fps 54,145psi and 99.0g at 2858 at 67,908psi out of a 26'' barrel. You should find an accurate load some where in between if the 1 in 10 twist will stablize those 240g MK's.

    Hope this helps!
     

  3. Jon A

    Jon A Well-Known Member

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    Something isn't right with those numbers. Quickload shows me only 62.2 KSI at 99 grains with a velocity of 2893. That's with the weighting factor at the default of .5--it should be lowered to more accurately represent this case. At .4 it shows only 59.7 KSI at 2914 fps, which is closer to what I've seen in reality.
     
  4. yote bomber

    yote bomber Well-Known Member

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    2900 fps with a 240... at under 60k psi would be an awesome load. Especially with the current availability of .300 RUM brass.
     
  5. jmatson

    jmatson Active Member

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    Jon you are correct! my weighting factor was set at .7, I don't have a 300
    RUM to compair any data. How do you like yours? I have been thinking about betting a Rem Sendoro.
     
  6. Jon A

    Jon A Well-Known Member

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    .7! Ouch! That'll do it! ;) I'm glad we figured out the discrepancy though.

    I still like it a lot. It's a great round.
     
  7. Varmint Hunter

    Varmint Hunter Well-Known Member

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    Stupid Question

    I'm sure this is a stupid question, but for the slow-of-mind; what is the weighting factor in Quickload? How (or why) is it applied to your input?
     
  8. Jon A

    Jon A Well-Known Member

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    It’s a measure of the percent of powder/gases that go “down the bore with the bullet.” For example, a straight walled case has a relatively small case capacity and large bore capacity. By the time the bullet exits the muzzle there’s only a very small percentage of gas left in the case—most of it is in the bore. On the contrary, for an “overbore” case, with a relativley large case capacity/small bore capacity, when the bullet exits there’s still a large amount of gas left in the case itself, a much smaller percentage will be traveling down the bore with the bullet.